aK^ 


v\\^^ 


A  MAISrUAL 


EXPERIMENTAL  PHYSIOLOGY 


STUDENTS  OF  MEDICINE. 


BY 

WINFIELD  S.  HALL,  Ph.D.,  M.D.  (Leipsic), 

PROFESSOR     OF    PHYSIOLOGY,     NORTHWESTERN     tTNIVERSITY    MEDICAL     SCHOOL;     PROFESSOR    OF 

PHYSIOLOGY,  WESLEY   HOSPITAL  SCHOOL   FOR   NURSES;    PROFESSOR   OF    PHYSIOLOGY, 

MERCY    HOSPITAL    TRAINING    SCHOOL    FOR    NURSES;     LECTURER    ON 

THE     PEIYSIOLOGY    OF    EXERCISE,    INSTITUTE    AND 

TRAINING   SCHOOL,    CHICAGO. 


WITH   89    ILLUSTRATIONS  AND  A   COLORED    PLATE. 


LEA  BROTHERS  &  CO., 
IMJJLADELPHIA    AND    NEW    YORK 


vvi?Trvin 


Entered  according  to  the  Act  of  Congress,  in  the  year  1904,  by 

LEA   BROTHERS   &   CO., 
In  the  OflBce  of  the  Librarian  of  Congress.     All  rights  reserved. 


DORNAN,    PRINTER. 


TO 

KATHAN  SMITH  DAVIS,  M.D.,  LL.D., 

RECENTLY  DECEASED  DEAN  EMERITUS  OF  THE  NORTHWESTERN 
UNIVERSITY    MEDICAL    SCHOOL, 

IN    HUMBLE    RECOGNITION    OF    THE    STIMULUS    WHICH    HE    GAVE    TO 

EXPERIMENTAL    MEDICINE    IN    AMERICA    AND    IN    GRATEFUL 

REMEMBRANCE  OF  THE  INSPIRATION  RECEIVED  FROM 

HIM   THIS    VOLUME    IS    RESPECTFULLY 

DEDICATED  BY  HIS  PUPIL, 

THE  AUTHOR. 


Digitized  by  tine  Internet  Arciiive 

in  2010  witii  funding  from 

Open  Knowledge  Commons  (for  the  Medical  Heritage  Library  project) 


http://www.archive.org/details/manualofexperimeOOhall 


-  PREFACE. 


This  volume  represents  the  accumulated  experience  of  a  decade 
in  the  presentation  of  experimental  physiology  to  medical  students. 

The  scope  of  the  book  has  naturally  been  determined  by  the  needs 
of  medical  students  who  are  preparing  for  the  practice  of  clinical 
medicine  and  surgery. 

The  preliminary  lessons  in  Cytology  are  presented  as  a  feature 
of  the  volume.  This  introductory  course  has  proven  to  be  a  most 
valuable  accompaniment  to  the  beginning  work  in  histology,  as  well 
as  a  most  substantial  foundation  to  general  physiology. 

The  arrangement  of  the  chapters  has  been  determined  by  two 
considerations:  (1)  the  degree  of  difficulty  of  the  technique,  and 
(2)  the  correlation  of  other  work  of  the  medical  course.  Cytology 
— the  first  chapter — involves  the  simplest  microscopic  technique, 
and  the  principles  of  cell  life  make  the  foundation  of  modern  medi- 
cine and  surgery.  Electro-physiology  involves  a  technique  not  too 
difficult  for  the  earlier  months  of  medical  study,  and,  at  the  same 
time,  it  forms  a  most  valuable  basis  for  the  experimental  work  that 
follows. 

The  order  of  the  chapters  on  Circulation,  Respiration,  Hema- 
tology, and  Digestion  may  easily  be  changed  to  suit  the  curriculum 
of  the  institution  where  the  course  is  given. 

The  exercises  have  for  years  been  furnished  my  students  in  the 
form  of  type-written  syllibi,  undergoing  almost  annual  revision. 
They  represent,  therefore,  a  gradual  evolution. 

At  no  time  during  this  development  of  a  practical  course  in 
experimental  physiology  has  the  author  lost  sight  of  the  fact  that 
his  [>iipils  were   j^reparing   for  cHnical  practice.     The  experimenls 

(v) 


VI 


PREFACE 


are  carefully  chosen  and  arranged  to  involve  a  considerable  amount 
of  surgical  work  and  to  present  to  the  student  those  fundamental 
facts  and  principles  of  physiology  which  form  the  basis  of  Internal 
Medicine. 

The  author  takes  this  opportunity  to  acknowledge  the  valuable 
assistance  of  his  associate,  Dr.  C.  J.  Kurtz,  who  prepared  the 
chapter  on  Normal  Hsematology,  and  of  Professor  Charles  H. 
Miller,  of  the  Department  of  Pharmacology,  for  his  assistance 
in  the  preparation  of  the  lessons  on  the  physiological  action 
of    drugs. 

W.  S.  H. 


CONTENTS, 


PAGE 

IXTRODUCTIOX 17 


PART    I. 

EXPERIMENTAL    GENERAL    PHYSIOLOGY. 

CHAPTER  I. 
Cytology. 

I.     Algae  or  Green  Plants  of  Low  Order 21 

II.     The  Yeast  Plant 26 

III.     Protozoa  or  One-celled  Animals 28 

IV.     Normal  Ciliary  Motion 31 

V.     Ciliary  Motion  Modified  bj^  the  Influence  of  CO2  and  Anaesthetics  33 

VI.     To  Detennine  the  Amount  of  Work  Done  by  Cilia 35 

CHAPTER  II. 

The  General  Physiology  of  Muscle  and  Nerve  Tissue. 

VII.     Electric  Apparatus  and  Units  of  Measurement 37 

VIII.     Batteries 41 

IX.     Methods  of  "S'arying  the  Strength  of  Current 43 

X.     Muscle-nerve  Preparation 46 

XI.     Electric  Stimulation  and  the  Myogram 50 

XII.     The  Typical  Mj-ogram,  Combined  Myograms,  and  Tetanus  54 

XIII.     The  Work  Done  by  a  Muscle     .      .' 55 

XrV.     To  Send  an  Electric  Current  into  a  Nerve  without    Response. 

Fleischl's  Rheonom 56 

XV.     To  Determine  the  Influence  of  Cathode  and  .\node  Poles  .58 

XVI.     Electrotonus  (to  Determine  the  Effect  of  a  Constaiil    Current 

upon  the  Irritability  of  a  Nerve) 61 

XVII.     The  Law  of  Contraction 64 

XVIII.     (a)  The  Capillary  Electrometer.    (/>)  The  M.thod  ol  (siiig  H  66 

XIX.     Electromotive  Phenomena  of  .Active  Muscle 60 


viii  CONTENTS 

PART    II. 

SPECIAL   PHYSIOLOGY. 

CHAPTER  III. 

The  Circulation  op  the  Blood. 

PAGE 

I.  The  Capillary  Circulation  and  the  Movements  of  the  Heart    .      .  73 

11.  The  Apex  Beat  and  the  Heart  Sounds 79 

III.  The  Flow  of  Liquid  through  Tubes  under  Constant  Pressure     .      .  81 

IV.  The  Flow  of  Liquids  through  Tubes  under  the  Influence  of  Inter- 

mittent Pressure         84 

V.     The  Laws  of  Blood  Pressure  Determined  from  an  Artificial  Cir- 
culatory   System Sft 

VI.     The  Radial  Pulse  and  the  Sphygmogram 88 

VII.     To  Determine  the  Arterial  Blood  Pressure  in  an  Animal  ....  91 

VIII.     The  Sphygmomanometer  and  Pulse  Pressure 93 

IX.  To  Determine  the  Influence  of  the  Vagus  Nerve  upon  the  Action 

of  the  Heart 95 

X.     To  Determine  the  Influence  of  the  Cardiac  Sympathetic  Nerves 

upon  the  Action  of  the  Heart 97 

XL     The  Influence  of  the  Vagus  and  the  Cardiac  Sympathetic  upon 

the  Arterial  Blood  Pressure 98. 

XII.     The  Blood  Pressure  in  the  Tissues 99 

XIII.  The  Action  of  Atropine  upon  the  Heart 101 

XIV.  The  Action  of  Pilocarpine  upon  the  Heart 102 

XV.     The  Action  of  Digitalis  upon  the  Heart 103 

XVI.     The  Action  of  Aconite  upon  the  Circulation 104 

XVII.     The  Action  of  Adrenalin  upon  the  Circulation 104 

CHAPTER  IV.     ' 

Respiration. 

I.  Thoracic  Movements.     Intrathoracic  Pressure     ......  106 

II.  Respiratory  Pressure.     Elasticity  of  the  Lungs.     Pneumatogram .  108 

III.  To  Study  the  Movements  of  the  Human  Thorax 110 

IV.  Lung     Capacity     (Chest    Measurements,    Respiratory    Pressure). 

Recording  of  Anthropometric  Data 113 

V.  The  Evaluation  of  Anthropometric  Data 115 

VI.     Quantitative  Determination  of  the  CO2  and  H2O  Eliminated  from 

an  Animal's  Lungs  in  a  Given  Time 117 

VII.     To  Determine  the  Amount  of  Oxygen  Consumed  by  an  Animal  in 

a  Given  Time 119 

VIII.     The  Respiratory  Quotient 121 

IX.     Respiration  under  Abnormal  Conditions 123 

X.  To  Determine  the  Influence  of  the  Phrenic  Nerve.     The  Normal 

Phrenogram 125 


CONTENTS  j^ 


CHAPTER  V. 

Xor:mal  H.ematology. 


PAGE 


Introduction  and  General  Directions 128 

I.  The  Counting  of  the  Blood  Corpuscles 13q 

A.  To  Count  the  Red  Blood  Corpuscles 132 

B.  To  Count  the  White  Blood  Corpuscles I35 

C.  To  Count  both  Red  and  White  Corpuscles  at  the  Same  Time  .      136 

D.  Centrifugalization  of  the  Blood.      To  Detennine  the  Relative 

Volume  of   Red  Corpuscles  and  Plasma.     To   Estimate  the 
Number  of  Red  Corpuscles  from  Their  Volume     ....     137 

II.  The  Estimation  of  the  Percentage  of  Coloring  Matter  in  the  Blood    .      138 

A.  Fleischl's  Ha^mometer 130 

B.  Gowers'  Haemoglobinometer 142 

C.  Dare's  Haemoglobinometer I44 

D.  Tallquist's  Hsemoglobinometer I45 

E.  Estimation  of  Hjemoglobin  by  Finding  the  Specific  Gravity    .  146 

III.  Examination  of  Fresh  Blood "  14§ 

A.  Coagulation  of  Nonnal  Blood 148 

B.  Microscopic  Examination  of  Blood 148 

C.  Spreading  Blood  for  Staining 150 

D.  Staining  Blood  Films 153 

E.  Differential  Counting  of  the  Cells I53 

IV.  Staining  Bone-marrow Igc 

CHAPTER  ^^I. 

D1GE.ST10N  AND  Absorption. 

Digestion l^g 

I.     The  Carbohydrates I57 

II.  Salivary  Digestion I59 

III.  The  Proteids lU 

IV.  (a)  Diffusibihty  of  Proteids.     (6)  Milk '      .  164 

V.     Gastric  Digestion 167 

VI.     Gastric  Digestion  (continued) 170 

VII.     Gastric  Digestion  (continued) I7I 

VIII.     The  Properties  of  Fats 172 

IX.     Intestinal  Digestion I74 

Absorption 170 

,   CHAPTER  VII. 

Vision. 

I.     DLssection  of  the  Appendages  of  the  Eye 178 

II.     Dissection  of  the  Eyeball I79 

III.  Physiological  Optics 181 

IV.  To  Determine  the  Focal  Distance  of  a  Lens 183 

V.     To  Locate  Experimentally  in  the  Mammalian  Eye-  the  Cardinal 

Points  of  the  Simple  Dioptric  System 185 


X  CONTENTS 

PAG 

VI.     Accommodation   and   Convergence 188 

VII.     Miscellaneous  Experiments 192 

VIII.     Perimetry 193 

IX.     Determination  of  Normal  Vision 196 

X.     The  Range  of  Accommodation 200 

XI.     Normal  Ophthalmoscopy  (Direct  Method) 201 

XII.     Normal  Ophthalmoscopy  (Indirect  Method) 203 

XIII.     Skiascopy 204 

CHAPTER  VIII. 

The  Physiology  op  the  Nervous  System. 

I.     ReflexAction 206 

II.     Reflexes  in  the  Human  Subject 208 

III.  The  Action  of  Strychnine  upon  the  Nervous  System     ....  210 

IV.  The  Action  of  Curare  upon  the  Nervous  System 212 

V.     The  Action  of  Veratrin  upon  the  Nervous  System 214 

VI.     Sensation 215 

VII.     Sensation  (continued) 218 

VIII.     Function  of  Spinal  Nerves 220 

CHAPTER  IX. 

The  Physiology  op  the  Mtjsculak  System. 

I.     Animal  Mechanics 222 

II.     Ergography 226 


APPENDIX. 

1.  Normal  Saline  Solution      . 229 

2.  Frog  Boards 229 

3.  The  Physiological  Operating  Case 229 

4.  Galvanic  Cells 230 

5.  Dry  CeUs 230 

6.  To  Curarize  a  Frog 231 

7.  To  Prepare  the  Kymograph  for  Work .'      .      .      .  231 

8.  A  Fixing  Fluid  for  Carbon  Tracings 231 

9.  Non-polarizable  Electrodes 232 

10.  The  Frog-heart  Lever 233 

11.  The  Respiratory  Cannula • 234 

12.  Tambours  (Receiving  and  Recording) .      .  '  234 

13.  The  Manometer  Talnbour 236 

14.  Thoracic  Cannulse 237 

15.  The  Stethograph 237 

16.  The  Chest  Pantagraph 238 

17.  The  Pneomanometer 240 


EXPERIMENTAL  PHYSIOLOGY. 


INTRODUCTION. 

The  general  method  of  presenting  the  subject  of  physiology  is  the 
same  as  that  followed  in  all  of  the  other  experimental  sciences,  viz., 
the  laboratory  method,  according  to  which  the  student  is  led  to  dis- 
cover for  himself  certain  facts  and  to  formulate  from  his  collected 
data  conclusions  which  represent  fundamental  principles  of  the 
science. 

This  method  of  presenting  the  experimental  sciences — chemistry, 
physics,  and  the  biological  sciences,  including  physiology,  psychology, 
pharmacology,  and  pathology — is  an  expensive  one,  both  as  to  the 
time  and  the  money  involved  in  it;  but  from  the  standpoint  of 
pedagogy  it  is  more  economical  than  the  text-book  method,  because 
it  leads  directly  and  surely  to  definite  results. 

In  answer  to  the  question  as  to  just  what  these  results  are  which 
follow  the  modern  laboratory  method  of  instruction,  it  may  be 
stated  first  of  all  that  it  cultivates  in  the  student  the  capacity  of  close 
and  accurate  observation;  it  affords  an  opportunity  for  valuable 
practice  in  the  systematic  recording  of  the  observations;  it  develops 
the  power  of  logical  thought  in  drawing  tenable  conclusions  from  the 
observed  data;  and,  in  the  formulation  of  conclusions,  it  stimulates 
the  ability  to  express  the  thoughts  in  concise  and  unambiguous 
terms.  In  the  second  place,  practice  of  this  kind  makes  the  student 
independent  and  furnishes  him  with  just  the  mental  equipment 
needed  for  later  life  in  whatever  line  his  activities  may  be  directed. 
If  such  an  education  is  more  important  for  one  profession  than 
another,  the  medical  profession  is  certainly  the  one  in  which  its 
importance  is  greatest.  The  physics,  chemistry,  and  biology  studied 
in  preparation  for  medicine,  and  the  physiology,  pharmacology,  and 
pathology  of  the  medical  course  should  give  the  student  a  most 
admirable  equipment  for  dealing  with  the  complex  problems  of 
clinical  practice. 

From  what  has  preceded,  it  will  have  been  noted  that  the  facts 
of  an  experimental  science  occupy  a  subordinate  position.  Facts 
are  only  stepping  stones  lea<ling  to  principles.  Prin("ij)les  are  impor- 
tant.    Quite  as  important  as  the  principles  to  wliich  the  facts  lead 

2 


18  EXPEEIMENTAL  PHYSIOLOGY 

is  the  method,  the  technique,  through  which  the  facts  are  observed. 
The  technique  guides  one's  hands  and  senses  in  the  study  of  new 
phenomena,  while  the  principles  already  mastered  guide  one's  mind 
in  dealing  with  the  facts  of  the  new  phenomena.  The  hand  and  the 
mind  working  with  technique  and  principles  make  the  equipment 
of  the  scientific  man  of  to-day. 

As  the  application  of  this  general  method  of  the  presentation  of 
physiology,  it  may  be  briefly  stated  that,  so  far  as  the  time  permits, 
the  student  discovers  for  himself  the  facts  and  draws  his  own  con- 
clusions, defending  them  against  the  criticism  of  others.  This  is 
supplemented  by  demonstrations  to  the  class,  in  which  each  student 
can  observe  phenomena  which  later  become  the  subject  of  general 
discussion.  Limitations  in  the  time  that  may  be  devoted  to  work 
in  the  laboratory  make  it  necessary  to  occasionally  discuss  phenomena 
and  principles  which  the  student  has  not  observed  and  formulated; 
but  these  discussions  have  the  purpose  of  permitting  a  more  Systematic 
presentation  of  the  subject  than  would  otherwise  be  possible,  and 
the  student  s  held  responsible  finally  for  what  he  has  observed  only. 
Regarding  Illustrations.  The  profuse  illustration  of  a  text-book 
is  in  perfect  accord  with  the  principles  of  pedagogy;  that  the  profuse 
illustration  of  a  laboratory  manual  is  the  reverse  is  evident  from 
the  following  considerations: 

The  laboratory  student  receives  from  the  demonstrator  the  material 
with  which  he  is  to  work.  If  he  receives  a  piece  of  apparatus  which 
is  new  to  him,  a  few  questions  or  hints  in  his  laboratory  manual 
will  lead  him  to  discover,  'from  an  examination  of  the  apparatus 
itself,  the  physical  and  mechanical  principles  involved  and  utilized 
in  it.  Most  students  will  spontaneously  make  drawings  showing 
the  essential  parts  of  all  instruments;  all  students  will  willingly  do  so 
if  required.  This  is  a  most  valuable  exercise  for  the  pupil,  which 
is  likely  to  be  omitted  if  the  manual  contains  cuts  of  the  apparatus. 
Nearly  every  exercise  requires  the  preparation  of  some  simple 
appliance — e.  g.,  a  frog  board  or  a  recording  lever — whose  adjust- 
ment will  be  much  facilitated  if  the  student  is  guided  by  a  figure  in 
his  manual,  but  a  model  which  the  demonstrator  has  set  up  will  be 
a  better  guide. 

I  have  often  seen  students  read  their  text  descriptive  of  some 
organ — e.  g.,  a  frog  heart — and  verify  its  statements  from  the  accom- 
panying figures,  leaving  almost  unnoticed  the  object  itself,  which 
lay  before  them.  A  few  brief  questions  or  hints  would  have  led 
them  to  discover  from  the  object  all  of  its  essential  features.  Dia- 
grammatic anatomical  figures  are  sometimes  useful  in  a  laboratory 
manual,  but  true  anatomical  pictures  are  worse  than  useless — they 
bar  the  student's  independent  progress.  If  his  laboratory  manual 
contains  illustrations  of  all  apparatus  and  tissues,  and  of  such  experi- 
ments as  admit  of  graphic  records,  the  student  makes  similar  draw- 


INTRODUCTION  19 

ings  in  his  notes,  either  unwilKngly  or  dependently — frequently 
both.  The  laboratory  work  is  thus  robbed  of  much  of  the  benefit 
it  is  intended  to  give  the  student.  Independence  and  originality 
are  completely  defeated  or  aborted,  except  in  the  case  of  the  rare 
student. 

If  the  laboratory  manual  contains  graphic  records  of  experiments, 
much  of  the  time  of  the  demonstrator  will  be  consumed  in  explaining 
to  the  students  why  the  same  physiological  functions  observed  with 
slightly  different  apparatus  and  under  slightly  different  circumstances 
may  ^-ield  tracings  which  differ  in  minor  detail  from  those  in  the 
book.  The  energies  of  both  demonstrator  and  students  will  thus 
be  partially  diverted  from  their  legitimate  channel. 

If  there  are  no  tracings  in  the  text,  students  will  naturally,  by 
comparison  of  their  tracings,  discover  the  essential  and  the  non- 
essential features  and  will  seek  the  cause  of  the  essential  features 
of  their  tracings.  After  the  student  has  made  these  independent 
discoveries  he  is  in  a  position  to  gain  the  maximum  profit  from  the 
comparison  of  his  own  tracings  with  those  which  others  have  taken, 
and  from  any  explanations  which  the  demonstrator  may  choose 
to  add. 

It  is  evident,  then,  that,  from  a  pedagogical  standpoint,  the  labo- 
ratory guide  should  be  sparsely  illustrated.  On  the  other  hand, 
the  student's  notes  should  be  profusely  illustrated. 

Regarding  Explanations.  It  may  be  well  to  introduce  this  topic 
by  a  statement  of  what  the  function  of  the  demonstrator  is  not.  It 
certainly  is  not  to  rob  the  student  of  the  pleasure,  exhilaration,  and 
benefit  of  the  independent  investigation  of  a  problem  by  introducing 
each  laboratory  period  with  an  enumeration  of  the  facts  and  prin- 
ciples which  the  work  of  the  day  is  expected  to  establish.  Such  an 
introduction  is  worse  than  useless.  The  desirability  of  even  asking 
the  attention  of  the  entire  class  to  introductory  remarks  on  the  gen- 
eral bearing  of  the  problem  in  hand  is  to  be  questioned.  If  the 
problem  is  well  chosen  and  the  work  in  the  physiological  laboratory 
properly  co-ordinated  with  that  in  the  recitation  room  and  lecture 
room  and  that  in  the  other  departments,  its  significance  will  be  at 
once  evident  to  the  intelligent  pupil.  If  the  introductory  talk  is 
omitted  the  prompt  student  may  begin  at  once,  upon  entering  the 
laboratory,  the  problem  of  the  day,  and  will  have  a  clear  gain  of  ten 
or  twenty  minutes.  Any  supplementary  introduction  or  hint  may 
most  profitably  and  economically  be  written  upon  the  blackboard. 

Most  of  the  experiments  given  in  this  book  cannot  conveniently 
be  performed  by  one  individual  working  alone.  After  some  experi- 
mentation it  has  been  found  most  advantageous  to  divide  the  class 
into  sections  not  exceeding  tiiirty  students,  and  to  subdivide  these 
sections  into  divisions  of  three  students  each.  Each  division  is 
assigned  a  table.     The  assistant  demonstrator  places  the  material 


20  EXPERIMENTAL  PHYSIOLOGY 

needed  for  one  day's  work  upon  the  table  or  where  it  is  readily 
accessible. 

Nothing  should  be  done  for  the  student  which  he  can  profitably 
do  for  himself.  A  small  class  with  less  limited  time  may  easily 
construct  much  apparatus  in  the  workshop.  No  class  is  so  large 
as  to  debar  the  members  from  the  privilege  of  setting  up,  adjusting, 
and  readjusting  all  apparatus. 

Nothing  should  be  told  a  student  which  he  can  readily  find  out 
for  himself.  The  function  of  the  demonstrator  is  to  guide  the 
student  by  questions  and  by  hints  to  discover  facts  and  to  formulate 
principles.  Extended  explanations  on  the  part  of  the  demonstrator 
may  instruct  the  student,  but  they  do  not  educate  him. 

Hints  to  the  Students.  It  is  a  general  principle  that  a  student 
gets  out  of  a  course  what  he  puts  into  it,  and  with  interest.  If  he 
invests  (1)  intellectual  capacity,  (2)  the  spirit  of  inquiry  and  inves- 
tigation, (3)  the  power  of  logical  reasoning,  and  (4)  the  power  to 
formulate  conclusions,  he  will  promptly  receive  interest  upon  the 
investment.  Further,  the  greater  the  investment  the  greater  the 
rate  of  interest.    This  may  seem  inequitable,  but  it  is  inevitable. 

The  value  of  taking  full  notes  of  laboratory  experiments  is  unques- 
tionable. The  following  hints  regarding  note-taking  may  be  advan- 
tageous : 

1.  Make  a  careful  description  of  each  new  instrument  with  which 
you  work. 

2.  Formulate  each  problem  definitely. 

3.  Describe  the  means  used  in  the  solution  of  the  problem. 

4.  Enumerate  the  facts  observed  through  the  help  of  the  means 
employed. 

f  J5.  Seek  for  and  note  causes  and  interrelations  of  the  facts  as 
far  as  possible. 

6.  Differentiate  the  essential  from  the  incidental. 

7.  Formulate  conclusions  from  the  collected  data. 

8.  Make  generalizations  as  far  as  they  are  justifiable. 

9.  A  good  note-book  should  possess  the  following  qualities: 

(a)  It  should  be  complete,  containing  an  account  of  every  problem 
studied. 

(6)  It  should  be  full,  containing  a  sufficient  amount  to  guide 
another  in  performing  the  same  experiments  and  in  verifying  the 
facts  and  conclusions  noted. 

(c)  It  should  be  logically  arranged. 

(d)  It  should  be  as  neat  and  artistic  as  the  student  can  make  it 
in  the  time  which  he  can  devote  to  it. 


PART    I. 
EXPERIMENTAL  GENERAL  PHYSIOLOGY. 


This  field  of  physiology  is  devoted  to  the  laboratory  observation 
of  the  general  activities  of  the  cells  and  tissues  of  living  plants  and 
animals.    The  study  of  cells  is  taken  up  under  the  head  of  Cytology. 


CHAPTER    I. 
CYTOLOGY. 

I.  ALG.ffl  OR  GREEN  PLANTS  OF  LOW  ORDER. 

Cytology  is  devoted  to  the  systematic  treatise  of  the  cell  as  a 
living  organism,  with  reference  to  form  as  well  as  to  function.  In 
the  unicellular  organisms  it  is  not  profitable  to  make  a  sharp  division 
between  the  discussion  of  the  form  and  function ;  they  should,  rather, 
be  discussed  together. 

Interesting  objects  for  the  illustration  of  cell  life  are  the  Alga?, 
which  are  representatives  of  the  lowest  sub-kingdom  of  plants. 
Some  of  the  Algffi  are  unicellular  and  some  are  multicellular.  Some 
are  motile  and  some  are  non-motile.  All  are  provided  with  chloro- 
phyll, which  is  a  coloring  matter,  usually  emerald-green,  though 
sometimes  a  brownish-green  and  sometimes  a  bluish-green.  Desmids, 
Protococcus,  and  Spirogyra  are  examples  of  non-motile  Alga*  possessed 
of  green  chlorophyll. 

Desmids.  These  little  plants  are  composed  of  a  single  cell,  which 
may  be  circular,  oblong,  or  crescentic.  Each  plant  is  divided  into 
.symmetrical  halves,  and  the  margins  and  the  distribution  of  the 
chlorophyll  are  symmetrical  and  ornamental. 

Protococcus.  The  green,  dust-like  coating  of  the  tree-trunks  and 
fence-posts  is  really  composed  of  myriads  of  minute  green  plants, 
which  are  composed,  like  the  desmid,  of  a  single  cell,  though  the.se 
cells  are  often  loosely  held  together  in  colonies  or  families  of  three 
or  four  a  short  time  after  the  young  are  formed.     Reproduction  in 


22 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


these  low  organisms  takes  place  by  what  is  called  fission.   This  process 
is  a  simple  division  of  the  cell  body  into  two  equal  portions.     The 


Fig.  1 


a,  Desmids.  Common  forms.  Shaded  portions  of  green  chlorophyll,  outer  envelope  of  cellu- 
lose. 6,  Protococcus.  Common  forms,  showing  reproduction.  A  cellulose  envelope  enclosing 
chlorophyll. 

first  undivided  cell  is  called  the  "mother  cell"  or  the  adult  cell, 
while  the  two  young  cells  resulting  from  the  fission  are  called 
"daughter  cells." 

Fig.  2 


h  Cy        Ch  s 

Spirogyra.  Two  cells  of  a  long  fibre  are  shown  :  iv,  cellulose  ceU  wall;  n,  nucleus  surrounded 
by  cytoplasm  {Cy),  which  sends  out  threads  to  the  cell  wall;  Ch,  chlorophyll  band  making  two 
and  one-half  spiral  turns  around  the  inside  of  the  cell  wall;  s,  starch  grain  surrounded  by  sev- 
eral oU  globules. 

Spirogyra.  This  plant  occurs  in  long,  delicate  threads  which 
represent  numerous  cylindrical  cells  joined  end  to  end.  It  receives 
its  name  from  the  spiral  disposition  of  its  chlorophyll.  Each  cell 
posesses  two  or  three  or  four  threads  of  chlorophyll,  which  are  wound 


CYTOLOGY 


23 


spirally  around  the  inside  of  the  transparent  cell  wall,  the  threads 
appearing  under  the  microscope  to  cross  and  recross  in  beautiful 
patterns.  In  reality,  however,  the  threads  do  not  touch  each  other. 
After  the  cool  October  weather  comes,  one  is  likely  to  find  in  the 
spirogyra  a  most  interesting  change  in  progress.  During  the  spring 
and  early  summer  the  spirogyra  grows  by  a  reproduction  of  its  cells 
by  fission;  these  cells  remain  together  and  the  reproduction  thus 
produces  the  long,  hair-like  threads.  As  these  delicate  threads  cannot 
live  over  winter,  nature  prepares  for  this  season  by  causing  a  new 
method  of  reproduction.  Two  cells  lying  side  by  side  put  out  pro- 
jections which  fuse  or  join  together,  making  a  communication  from 
one  cell  into  the  other.  Through  this  communication  the  contents 
of  one  cell  flows  into  the  other  and  the  contents  of  both  cells  are  thus 
mixed.    This  process  is  called  "conjugation."     After  the  conjugation 


Fig.  3 


Dialoms.     Having  silicious  envelopes  or  shells  outside  the  exochrome. 


the  new  mass  forms  a  thick  cellulose  covering  and  passes  into  a 
"resting  stage"  for  the  winter.  With  the  warmth  of  returning 
spring  the  cellulose  shell  is  burst  and  the  new  plant  starts  its 
summer  growth. 

Motion  is  so  characteristic  of  the  higher  animals  and  a  lack  of 
voluntary  motion  .so  characteristic  of  higher  plants,  one  naturally 
a.ssociates  motion  with  animal  life.  But  many  of  the  lower  orders 
of  plants  have  the  power  of  locomotion,  while  many  of  the  lower 
animals — e.  g.,  corals  and  barnacles — are  as  fixed  as  a  tree. 

Among  the  algaj  (motile)  are  diatoms  and  oscillaria. 

Diatoms.  These  are  one-celled  plants  possessing  a  brownish- 
f^cf-n  chlorophyll  and  encased  in  two  delicate  silicious  scales,  which 
fit  together  like  a  box  and  its  cover.  They  are  boat-sliaj)ed  and 
move  slowly  across  th(;  field  of  the  microsco[)e,  puslunl  along  l)y  a 


24 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 
Fig.  4 


J  2 


OscUlaria.     a,  enlarged  fibre;  6,  same,  showing  oscillation  from  position  1  to  position  2,  in 

sunlight. 

Fig.  5 


Swarm  spores,     a,  of  Acetabularia;  c,  of  Botrydium;  e,  of  Ulotrix. 


CYTOLOGY  25 

trail  of  mucus  which  they  give  out  in  a  continuous  stream  when  in 
motion. 

A  high  magnification  usually  shows  fine  transverse  lines  across 
the  diatom  shell.  These  lines  are  so  fine  in  some  species  of  diatom 
that  these  little  plants  serve  as  test  objects  to  test  the  optical  powers 
of  a  microscope. 

Oscillaria.  The  oscillaria  is  a  thread-like  motile  alga,  provided 
with  a  bluish-green  chlorophyll.  The  threads  are  not  long  and  the 
motion  consists  in  a  jerky,  oscillatory  movement  of  the  ends  of  the 
threads. 

Swarm  spores  of  the  fresh-water  algae  are  unicellular  and  are  the 
best  examples  of  motile  plants  of  the  lower  order.  The  first  thought 
that  comes  to  one  while  watching  the  active  little  plants  is.  Why 
do  they  move?  The  animal  lives  upon  plants  or  other  animals  and 
must  be  provided  with  some  means  of  catching  its  food.  The  green 
plant  lives  upon  carbon-dioxide  gas  and  water,  with  the  salts  dis- 
solved in  the  water.  But  as  the  swarm  spores  live  in  water  in  which 
COj  and  mineral  salts  are  dissolved,  why  should  they  be  endowed 
with  locomotion? 

Laboratory  Exercises. 

1.  Appliances.  ^Microscope  with  high  and  low  power;  slides,  plain 
and  celled;  cover-glasses;  pipette. 

2.  Preparation.  Several  well-stocked  aquaria,  stocked  with  pond 
scum,  slime,  ooze,  and  pond  water  gotten  from  stagnant  ponds  which 
lie  in  not  too  close  proximity  to  a  manufacturing  district  or  railway. 
By  stocking  aquaria  from  different  ponds  one  is  likely  to  find  all 
the  above-named  forms  (except  protococcus)  and  perhaps  many 
other  forms.  Keep  the  aquaria  near  the  windows,  where  they  will 
get  the  warm  sunshine  during  the  day.  In  addition  to  the  above, 
one  will  do  well  to  prepare  an  infusion  of  hay  and  keep  the  same 
in  a  .500  c.c.  Vjeaker.  The  amoeba,  paramoecium,  and  dileptus  are 
likely  to  appear  in  the  liquid  after  a  few  days,  while  it  will  swarm 
with  myriads  of  bacteria. 

.3.  Observations.  (1)  Take  a  drop  of  water  from  near  the  top  or 
bottom  of  one  of  the  aquaria,  place  it  upon  a  slide,  put  a  clean 
cover-glass  gently  over  it,  and  focus  under  the  low  power  of  the 
microscope.  Look  for  any  of  the  organisms  above  described.  As 
the  aquaria  will  probably  differ  somewhat  the  one  from  the  other 
in  the  organisms  which  they  contain,  the  student  will  do  well  to 
examine  the  contents  of  all  the  aquaria.  Study  all  forms  of  life. 
Determine,  if  possible,  in  the  first  place  whether  an  organism  is 
plant  or  animal.  If  it  seems  to  be  plant,  determine  whether  or  not 
it  represents  one  of  the  common  algie  above  described.  If  so,  make 
a  careful  study  of  it. 


26  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

(2)  Draw  a  careful  figure  of  all  forms  studied,  making  the  figure 
large  enough  to  show  the  details  of  structure  clearly.  Indicate  in 
the  figure  the  location  of  the  chlorophyll.  If  a  nucleus  or  other 
prominent  mass  is  seen  within  the  cell,  locate  it  carefully  in  the 
drawing. 

(3)  Note  carefully  whether  or  not  the  organism  moves.  If  it  does, 
determine  the  cause  of  the  movement  and  describe  it  minutely. 


II.  THE  YEAST  PLANT. 

The  yeast  plant  (saccharomyces)  belongs  to  a  fungi.  The  fungi 
and  the  algae  belong  to  the  lowest  sub-kingdom  of  plants — the 
Thallophytes — which  are  characterized  by  the  absence  of  root,  stem, 
and  leaf.  The  student  will  remember  that  all  the  algse  which  he 
has  studied  have  possessed  chlorophyll  or  green  coloring  matter. 
This  is  true  of  the  algse  in  general.  The  fungi,  however,  have  no 
green  coloring  matter.  The  toadstool  is  a  fungus,  and  it  is  wholly 
without  the  green  color  which  most  plants  possess.  The  yeast  plant 
is  a  fungus  and  it  has  no  chlorophyll. 

What  is  the  work  which  the  chlorophyll  does  for  the  green  plants? 

How  does  the  yeast  plant  get  its  living? 

Laboratory  Exercises. 

1.  Put  a  bit  of  fresh  yeast  about  as  large  as  the  head  of  a  pin 
upon  a  glass  slide,  mix  it  with  normal  saline  solution  (0.6  per  cent. 
NaCl  in  aq.  dest.)  and  study  under  high  power.  Draw  and  describe 
the  cells.  The  yeast  reproduces  by  budding  or  gemmation.  It 
reproduces  also  by  the  formation  of  internal  spores  (ascosporse) 
(Fig.  6).  Let  your  figure  show  various  forms  and  combinations  of 
cells.  Is  the  protoplasm  of  the  cells  homogeneous  or  is  it  granular? 
Is  a  reticulum  visible  under  your  microscope? 

2.  Put  a  piece  of  fresh  yeast  about  the  size  of  a  hazelnut  into 
30  c.c.  of  Pasteur's  fluid,  and  stand  this  for  a  period  of  one  hour 
in  an  incubator  kept  at  a  temperature  of  35°  to  40°  C. 

Pasteur's  Fluid: 

Potassium  phosphate 2.0  grams. 

Calcium,  phosphate 0.2 

Magnesium^  sulphate 0.2 

Am^m.onium  tartrate           .......  10.0 

Saccharose  (cane-sugar)    .......  150.0 

Aqua q.  s.  ad  1000.0 

After  a  half  or  three-quarters  of  an  hour  remove  the  yeast  from 
the  incubator  and  examine  the  mixture  carefully.  Note  the  rapid 
escape  of  bubbles  from  the  liquid.     If  the  liquid  be  placed  in  a 


CYTOLOGY 


27 


small  flask  and  a  tube  led  from  the  closed  flask  into  a  solution  of 
Ca(OH)2  the  character  of  the  gas  will  be  revealed — it  is  carbon 
dioxide,  COj. 

The  cane-sugar  gives  the  Pasteur  solution  a  sweet  taste.  Taste 
an  yeast  mixture  that  has  been  in  the  incubator  twenty-four  hours. 
It  has  lost  its  sweetness  and  gained  the  taste  of  alcohol  and  CO2. 
The  yeast  plant  consumes  sugar  and  breaks  it  up  to  CO2  and  H2O. 
The  alcohol  and  CO3  are  waste  products  which  the  yeast  throws 
out  because  they  are  useless  to  it. 


Fig.  6 


Saccharomyces,  or  yeast  plant:  o,  isolated  yeast  cells;  b,  c,  gemmation;  d,  endogonidia  or 
ascosporae;  e,  budding  of  the  endogonidia. 


3.  Place  5  c.c.  of  the  yeast  mixture  in  a  test-tube  and  insert  the 
tube  in  boiling  water  for  a  minute,  or  hold  the  tube  over  a  Bunsen 
burner  until  the  mixture  comes  to  a  boil.  What  is  the  influence  of 
the  heat  upon  the  life  of  the  yeast?  Is  there  any  evidence  that  the 
yeast  has  been  killed;  if  so,  what? 

4.  Place  5  c.c.  of  an  active  mixture  in  a  test-tube  and  add  alcohol 
(95  per  cent.)  drop  by  drop  until  a  change  is  noticed  in  the  activity 
of  the  yeast.  Has  the  yeast  been  stimulated?  If  not,  what  has  the 
effect  been?     Account  for  the  results. 

5.  To  another  5  c.c.  of  active  yeast  mixture  add  crystals  of  common 
salt,  stirring  gently  to  cause  solution,  and  note  results. 


28 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


III.   PROTOZOA  OR  ONE-CELLED  ANIMALS. 

We  come  now  to  an  entirely  different  order  of  beings — the 
protozoa,  or  one-celled  animals.  They  live  in  the  water  and  feed 
upon  unicellular  plants.  They  sometimes  contain  granules  of 
chlorophyll,  sufficient  in  quantity  to  give  them  the  appearance  of 
motile  plants,  but  the  chlorophyll  has  been  taken  up  with  the  plants 
which  they  have  eaten.  Chlorophyll  thus  absorbed  is  retained  only 
a  short  time  and  is  then  excreted.  The  protozoa  are  classified  as 
follows : 

Fig.  7 


Amaha.  a,  at  rest ;  6,  extending  pseudopodia  in  search  of  food;  c,  food  enclosed;  d,  repro- 
duction by  fission,  beginning  with  division  of  nucleus  and  vacuole;  e,  cytoplasm  dividing; 
/,  reproduction  complete. 

Protozoa.     One-celled  animals. 

1.  Rhizopoda,  protozoa  possessing  bodies  of  changeable  shape. 

(a)  Helizoa,  naked  rhizopoda.     Ex.  amoeba  (Fig.  7). 
(6)  Foraminifera,  marine  rhizopoda  with  porous  shells. 
(c)  Radiolaria,  marine  rhizopoda  with  concentric  spherical 
shells. 

2.  Infusoria,  protozoa  possessing  bodies  of  fixed  shape. 

(a)  Flagellata,  infusoria  that  swim  with  a  whip-like  flagellum. 

Ex.  Euglena  (Fig.  8). 
(6)  Ciliata,  ciliated  infusoria  with  mouth  and  anus.    Ex.  Para- 

moecium  (Fig.  9).    Vorticella  (Fig.  10). 


Laboratory  Exercises. 

1.  Appliances.     Microscope  with  j-inch  to  ^-inch  objective;  cell 
slides;  covers;  aquaria  well  stocked  with  protozoa;  drop-tubes;  filter 


CYTOLOGY 


29 


Fig.  8 


paper  and  absorbent  cotton;  50  per  cent,  alcohol;  ether;  saturated 
salt  solution;  aqueous  10  per  cent,  solutions  of  iodine,  of  tannic 
acid,  of  picric  acid,  and  of  nitrate  of  silver. 

2.  Observations.  Place  a  small  drop  of  water  containing  euglense, 
amoebae,  paramcecia,  vorticellse,  or  other  protozoa  on  the  center  of 
a  perfectly  clean  cover-glass.  If  there  are 
any  drops  of  fibrous  algae,  as  conferva  or 
spirogyra,  the  cover  may  be  inverted  upon 
a  clean  slide  and  the  animals  studied.  If, 
however,  there  are  no  plants  present,  the 
cover-glass  may  be  supported  upon  a  hair 
laid  across  the  slide,  otherwise  the  cover  will 
settle  down  upon  the  animals  and  prevent 
their  free  movements. 

After  the  cover  is  properly  supported  and 
the  organisms  focused,  make  a  careful  studv 
of  the  forms  present,  describing  their  struc- 
ture and  such  activities  as  are  observed. 

To   Determine   the   Influence  of  Carbon 

Dioxide  upon  the  Activity  of  Animal 

Cells. 

1.  Appliances.  ^Microscope  with  high 
power;  ventilated,  deep  celled  slide;  ventila- 
ting apparatus,  consisting  of  reservoir,  siphon, 
and  pressure  bottle  with  connections  as  shown 
in  Fig.  11  (p.  34) ;  aquarium  stocked  with  pro- 
tozoa; normal  saline  solution  (NaCl  0.6  per 
cent.);  CO2  gas  generator. 

2.  Exercises.  (1)  (a)  Set  up  the  ventila- 
ting apparatus  as  shown  in  Fig.  11.  The 
slide  should  be  clamped  upon  the  stage  of 
the  microscope  with  the  help  of  the  stage 
clips.  Disjoin  the  CO2  flask  at  S  and  d; 
fill  and  clamp  the  siphon;  fill  the  flask  with 
COj  from  the  generator  and  replace  it  in 
the  apparatus;  close  both  clamps. 

Mount  a  hanging  drop  of  protozoa  from  the  aquarium;  focus 
under  high  power.  While  watching  the  movements  of  the  protozoa 
loosen  the  siphon  clamp;  after  the  siphon  starts,  loosen  the  gas 
clamp  slightly  to  admit  a  little  of  the  COj.  If  after  a  half-minute 
or  more  no  appreciable  change  takes  place  in  the  rate  of  movement 
of  the  cilia,  repeat  the  dose  of  gas.  What  is  the  effect  of  CO.^  upon 
the  activity  of  protozoa? 

(b)  After  the  effect  of  the  gas  has   become  apparent,  clamp  the 


Euglena  viridis.     A  flagellate 
infusorian. 


30 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


tube  at  S;  disjoin  the  gas  tube  at  d,  and  gently  draw  air  through  the 
cell,  thus  ventilating  it  and  restoring  practically  the  normal  condition. 
Do  the  cells  resume  their  normal  movement? 

(c)  How  many  times  may  the  cells  be  brought  under  the  influence 
of  the  CO2  and  then,  by  ventilation,  be  brought  to  the  normal  con- 
dition again? 

Do  you  see  evidence  that  any  of  the  animals  eat  green  plants? 
Do  you  note  any  of  the  reproductive  changes  in  any  organism? 
What  is  the  method  of  locomotion  of  the  forms  studied?  Do  the 
organisms  respond  to  such  mechanical  stimuli  as  a  gentle  rapping 
upon  the  slide  with  pencil  or  scalpel? 

Fig.  9 


Paramoecium  bursarium.    ec,  ectoplasm;  en,  endoplasm;  n,  nucleus  with  nucleolus;  a,  vestibule; 
o,  oral  aperture;  os,  oesophagus;  v,  vacuoles;  /,  ingested  food. 


(2)  With  a  drop-tube  place  a  drop  of  saturated  salt  solution  at  one 
edge  of  the  cover.  By  placing  a  piece  of  dry  filter  paper  at  the 
other  edge  of  the  cover,  the  capillary  attraction  of  the  paper  will 
draw  the  salt  solution  under  the  cover  and  thus  mix  it  with  the 
aquarium  water.  Study  the  effect  of  this  upon  the  animal  organism 
present  and  describe  minutely  everything  observed. 

(3)  Place  a  drop  of  50  per  cent,  alcohol  beside  the  cover-glass  and 
draw  it  under  as  described  above.    Note  results  as  above. 

(4)  In  a  similar  way  study  the  effect  of  iodine,  tannic  acid,  picric 
acid,  and  nitrate  of  silver. 

(5)  Take  a  deep-celled  slide;  upon  the  top  of  the  cell  invert  a  clean 
cover-glass  to  which  is  clinging  a  "hanging  drop"  taken  from  an 
aquarium  well  stocked  with  protozoa.  The  "hanging  drop"  should 
be  a  small  one  for  two  reasons:   (1)  objects  within  a  small  hanging 


CYTOLOGY 


31 


Fig.  10 


drop  are  more  readily  focused  with  a  high-power  objective;  (2)  if 
the  drop  is  small,  vapors  penetrate  more  readily  to  the  organisms. 
Focus  upon  the  drop  through 
the  cover-glass.  If  you  find 
active  protozoa,  study  their 
movements  and  note  the  de- 
gree of  activity  of  these  move- 
ments. 

Prepare  a  little  roll  of  ab- 
sorbent cotton  about  as  large 
as  a  pea,  saturate  it  with  50 
per  cent,  alcohol  and  place 
it  in  the  bottom  of  the  cell, 
at  one  side  in  order  not  to 
interrupt  the  light. 

Replace  the  cover-glass 
and  focus  again  upon  the  or- 
ganisms which  you  studied 
a  few  moments  before.  Note 
carefully  whether  or  not 
there  is  any  change  of  ac- 
tivity; if  so,  describe  min- 
utely what  you  have  ob- 
served. 

(6)  If  a  change  in  activity 
is  noticed,  remove  the  cover- 
glass,  expose  it  to  the  air  for 
two  or  three  minutes,  then 
invert  it  over  a  clean,  dry 
cell,  and  note  whether  there 
is  a  partial  or  complete  return 
to  the  normal  activity. 

(7)  Repeat  this  experiment, 
using  fresh  protozoa  and 
ether  (50  per  cent.)  instead 
of  alcohol. 


^  B 

Vorticella.  A,  expanded  condition;  n,  nucleus;  Vc, 
vacuole;  w,  peristome;  Va,  vestibule;  g,  gemma; 
p,  pedicle;  B,  contracted  condition.  The  pedicle  is 
thrown  into  a  spiral  coil,  drawing  the  body  to  the 
point  of  attachment. 


(8)  Repeat,  using  dilute  ammonia  or  oil  of  peppermint. 


IV.  NORMAL  CILIARY  MOTION. 

1.  Appliances.  Microscope,  cell  slide,  and  cover-glass;  physio- 
logical operating  case  (see  Appendix,  3);  normal  saline  solution; 
frog  or  clam;  camel's-hair  brush  or  absorbent  cotton;  frog  board 
(.see  Appendix,  2)  and  cork  board. 

2.  Preparation.  To  Pith  a  Frog.  (1)  Grasj)  it  with  the  left  hand, 
holding  the  legs  extended,  one  on  either  side  of  the  little  finger,  in 


32  EXPERIMENTAL  GENERAL  PHYSIOLOGY. 

such  a  way  as  to  bring  the  dorsum  of  the  frog  toward  the  palm  of 
the  hand. 

(2)  With  the  thumb  and  index  finger  grasp  the  frog's  nose  and 
press  it  ventrally. 

(3)  Place  the  point  of  a  narrow-bladed  scalpel  in  the  median 
dorsal  line  over  the  space  between  the  occiput  and  atlas — i.  e.,  over 
the  occipito-atlantal  membrane.  This  point  is  most  readily  located 
by  using  the  eyes  as  a  landmark. 

The  occipito-atlantal  membrane  lies  at  the  apex  of  an  equilateral 
triangle  whose  base  has  its  extremities  in  the  center  of  the  cornese 
and  whose  apex  extends  posteriorly.  Having  located  the  point  of 
incision,  press  the  knife  through  the  skin,  the  intervening  connective 
tissue  and  the  occipito-atlantal  membrane,  and  cut  the  spinal  cord 
transversely.     Withdraw  the  knife. 

(4)  Insert  the  apex  of  a  slender  probe  or  of  a  blunt  needle  into 
the  incision,  turning  it  sharply  forward  so  as  to  enter  the  cranial 
cavity.  By  sweeping  the  distal  end  of  the  probe  from  side  to  side 
the  contents  of  the  cranial  cavity  may  be  functionally  destroyed. 
When  it  is  required  simply  to  pith  a  frog  it  is  understood  that  the 
operation  is  complete  as  described  above.  It  may,  however,  fre- 
quently be  necessary  to  destroy  the  spinal  cord  as  well  as  the  brain. 
To  accomplish  this  insert  the  needle  as  described  under  (4);  but 
turn  the  point  of  the  probe  so  that  it  shall  enter  the  neutral  canal 
of  the  vertebrse.  Pass  it  along  this  canal  to  a  point  nearly  opposite 
the  anterior  end  of  the  ilia.    Withdraw  the  probe. 

A  pithed  frog  can  suffer  no  pain,  but  will  respond  reflexly  to 
certain  stimuli.  A  pithed  frog  whose  spinal  cord  is  destroyed  cannot 
with  the  skeletal  muscles  respond  reflexly  to  any  stimuli.  Having 
pithed  the  frog  destroy  its  spinal  cord,  pin  it  to  a  frog  board,  with 
dorsum  down  and  legs  extended. 

To  Remove  the  (Esophagus  of  a  Frog.  (1)  Place  the  head  of  the 
frog  nearer  to  the  operator.  With  forceps  lift  the  mandible  and  with 
stronger  scissors  sever  the  whole  floor  of  the  mouth  transversely 
and  as  far  posteriorly  as  possible.  Divide  the  skin  in  the  median 
line  as  far  posteriorly  as  the  pubes. 

(2)  Separate  the  two  lateral  halves  of  the  sternum  by  dividing 
the  median  sternal  cartilage  and  carry  the  incision  through  the 
xiphoid  appendix  and  abdominal  walls.  Withdraw  the  pins  which 
fix  the  anterior  extremities ;  separate  the  lateral  halves  of  the  sternum 
by  lateral  traction  upon  the  anterior  limbs. 

(3)  With  the  forceps  grasp  a  fold  of  the  mucous  membrane  which 
surrounds  the  puckered  anterior  end  of  the  oesophagus.  While 
making  gentle  traction  with  the  forceps  make,  with  fine  scissors, 
a  circular  incision  through  the  mucous  membrane  surrounding  the 
opening  of  the  oesophagus. 

(4)  Grasp  the  pyloric  end  of  the  stomach,  sever  the  duodenum, 


CYTOLOGY  33 

lift  the  stomach  up  vertically  above  the  sternum,  and  make  moderate 
traction.  The  delicate  and  elastic  submucosa  aljout  the  end  of  the 
oesophagus  will  yield  to  the  traction  and  the  whole  oesophagus  will 
be  readily  separated  from  the  surrounding  tissues  and  wholly  removed 
from  the  frog. 

(5)  Open  the  stomach  and  oesophagus  by  means  of  a  longitudinal 
incision  through  their  walls;  stretch  them  on  a  cork  board,  fixing 
with  pins,  and  gently  wash  off  mucus  with  normal  saline  solution 
and  camel's-hair  brush.  Remove  the  excess  of  liquid  with  the  help 
of  filter  paper. 

3.  Obseirations.  (1)  Place  a  small  piece  of  cork  upon  the  anterior 
end  of  the  oesophagus.  Does  the  cork  move?  If  so,  in  what  direction 
and  at  what  rate? 

(2)  Will  the  cork  pass  over  the  boundary  line  between  oesophagus 
and  stomach,  and  will  it  move  over  the  surface  of  the  stomach? 

(3)  To  determine  the  cause  for  the  movement  of  the  cork,  cut  a 
minute  portion  of  mucous  membrane  from  the  crest  of  one  of  the 
folds,  place  it  in  a  hanging  drop  of  saline  solution  mounted  over  a 
cell  slide,  and  examine  with  a  microscope.  If  the  preparation  has 
been  properly  made  the  margin  of  the  tissue  should,  at  certain  points, 
show  the  cause  for  the  phenomena  above  observed.  Study  the 
character  of  the  ciliary  movements.     Describe. 

(4j  Study  ciliary  movement  with  higher  power.  It  is  probable 
that  the  first  preparation  is  not  suited  to  observation  with  a  high 
power.  If  the  cilia  cannot  be  readily  brought  into  focus,  prepare 
a  second  one  as  follows:  From  the  ciliated  surface— clam-gill  or 
frog-oesophagus — scrape  a  few  epithelial  cells  with  the  point  of  a 
scalpel,  place  the  minute  bit  of  tissue  upon  a  cover-glass,  add  a  small 
drop  of  saline  solution,  gently  tease  the  tissues  with  needles,  and  invert 
the  cover  upon  a  slide,  allowing  one  edge  to  rest  upon  a  hair,  to 
avoid  undue  pressure  upon  the  tissue. 

Focus  under  high  power  (300  to  GOO  diam.).  If  the  preparation 
is  successful,  groups  of  ciliated  cells  may  be  seen  and  the  character 
of  the  ciliarv  movement  studied. 


V.    CILIARY  MOTION   MODIFIED   BY   THE    INFLUENCE   OF   CO, 
AND  ANESTHETICS. 

1.  Appliances.  In  addition  to  the  appliances  enumerated  in  the 
foregfjing  lesson  one  needs  a  ventilating  apparatus  with  ventilated 
cell  slide.     Ciiloroform,  ether,  ab.solute  alcohol. 

Fill  the  glass  flask  full  of  water  and  displace  it  with  COj  gas. 
Fill  the  siphon  and  adjust  ap[)aratus  as  shown  in  Fig.  11.  During 
any  readjustments  of  the  ap|)aratus  the  siphon  may  be  ke])t  filled 
and  ready  for  action  by  putting  on  a  screw  clamp  at  S.     Through 

3 


34 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


varying  the  height  of  the  receptacle  into  which  the  siphon  dips  or 
through  adjustment  of  the  screw  clamp  or  of  the  spring  clamp  at  d, 
the  pressure  and  the  rate  of  flow  of  gas  are  under  perfect  control. 
Prepare  a  specimen  of  cilia  for  observation  with  a  low-power  micro- 
scope. (Great  care  must  be  taken  to  remove  all  of  the  mucus,  other- 
wise the  CO2  may  have  little  effect  on  the  cilia.)  Bring  a  good 
specimen  into  the  field,  focus  the  microscope,  and  observe  the  rate 
and  character  of  ciliary  movement.    Remove  screw  clamp  at  S. 


Fig.  11 


Apparatus  for  forcing  a  stream  of  gas  or  vapor  through  a  microscopic  slide  chamber. 
(For  description  see  text.) 


2.  Observations,     (a)  The  effect  of  CO2  upon  ciliary  activity. 

(1)  While  observing  closely  the  normal  action  of  the  cilia,  press 
the  spring  clamp  gently  for  a  few  moments.  If  after  half  a  minute 
or  more  no  noticeable  change  takes  place  in  the  rate  of  movement 
of  the  cilia,  repeat  the  dose  of  gas.  What  is  the  effect  of  CO2  gas 
upon  the  activity  of  cilia? 

(2)  After  the  effect  of  gas  has  become  apparent,  clamp  the  tube 
at  d;  disjoin  at  glass  tube  beyond  and  gently  draw  air  through  the 
cell,  thus  ventilating  it  and  restoring  practically  the  normal  condition. 
Do  the  cilia  resume  the  normal  movement? 

(3)  How  many  times  may  the  cilia  be  narcotized  to  the  point  of 
complete  cessation  of  activity  and  then  by  ventilation  be  revived 
again? 

(b)   The  effect  of  chloroform  gas  upon  ciliary  activity. 

(4)  Clamp  tube  at  S;  remove  flask  from  apparatus;  fill  flask  with 
water  to  expel  CO2;  empty.  (Suspend  in  the  flask  a  wad  of  cotton 
saturated  with  chloroform  or  ether.)  Make  a  new  preparation  of 
cilia  and  observe  normal  movement. 


CYTOLOGY 


35 


Allow  the  chloroform  gas  to  flow  for  a  moment  into  the  cell. 
Note  the  effect  of  chloroform  upon  ciliary  activity. 

(5)  How  many  times  may  the  cilia  be  narcotized  with  chloroform 
and  revived  again  through  ventilation? 

(6)  Repeat  (4)  with  ether  in  place  of  chloroform. 

(7)  Repeat  (5)  w^ith  ether  in  place  of  chloroform, 
(c)  Determine  the  action  of  alcohol  vapor  upon  cilia. 

VI.   TO  DETERMINE  THE  AMOUNT  OF  WORK  DONE  BY  CILIA. 

1.  Appliances.  Physiological  operating  case;  frog  board;  cork 
board  10  cm.  long  by  5  cm.  wide;  a  centimetre  rule;  a  block  of  wood 
4  cm.  or  5  cm.  in  height;  a  set  of  weights  as  follows:  50  mgm.  and 
100  mgm.,  3  mm.  square;  also  100  mgm.  and  200  mgm.,  5  mm. 
square. 

Fig.  12 


Apparatus  for  use  in  determining  the  amount  of  work  done  by  cilia.     (For  description 

see  text.) 


2.  Preparation.  Pith  a  frog  and  destroy  cord.  Dissect  out 
Of?sr)phagus  and  stomach  as  directed  in  Lesson  IV.  Fix  to  cork 
board  so  that  the  long  axis  of  the  o'sophagus  shall  be  parallel  with 
the  long  axis  of  the  board. 

3.  Operation.  Wash  off  ciliated  surface,  remove  surj)liis  moisture 
with  filter  paper,  and  place  a  lead  weight  gently  on  the  anterior  end 
of  the  O'sophagus. 


36  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

The  incline  of  the  ciliated  surface  may  be  changed  by  resting  it, 
at  different  angles,  against  the  block  of  wood  as  shown  in  Fig.  12. 

4.  Observations.  (1)  If  the  preparation  is  successful,  the  piece  of 
metal  will  be  slowly  carried  up  the  incline.  Should  it  fail,  a  thinner 
piece  of  lead  or  a  new  preparation  may  succeed.  With  a  given 
incline,  is  the  small  piece  of  lead  carried  more  rapidly  than  the 
large  piece? 

(2)  If  IF  =  work  done,  gr= weight  in  milligrams  and  A  =  height  in 
millimetres,  then  W=g  X  h  would  give  the  work  in  milligram- 
millimetres. 

(3)  Determine  the  distance  through  which  the  weight  is  carried 
in  a  unit  of  time  (one  minute  is  a  convenient  unit  of  time  to  use), 
when  the  incline  is  placed  as  shown  in  Fig.  12. 

(4)  With  the  apparatus  so  adjusted,  what  is  the  value  of  h  when 
the  distance  which  the  weight  moves  is  1  cm.  ?  Does  the  thickness 
of  the  cork  board  need  to  be  considered? 

(5)  What  is  the  work  per  minute,  expressed  in  milligram- 
millimetres? 

(6)  What  is  the  work  per  minute,  expressed  in  gram-centimetres? 

(7)  What  is  the  work  per  minute,  expressed  in  ergs?  (An  erg= 
1  dyne  X  1  cm.;  1  dyne=  1  gm.  divided  by  981  or  1  gm.  =  981  dynes; 
therefore,  1  gram-centimetre — 981  dyne-centimetres.  To  express 
work  in  ergs  find  the  gram-centimetres  and  multiply  by  981.) 

(8)  What  is  the  "activity"  of  the  cilia  in  work  per  second? 
Divide  ergs  per  minute  by  60  to  get  ergs  per  second. 

(9)  Using  the  same  incline  of  the  cork  board,  with  which  weight 
do  you  get  the  greatest  activity? 

(10)  Using  the  weight  which  gives  the  greatest  activity,  find  the 
degree  of  incline  which  yields  the  greatest  activity  of  cilia. 

(11)  What  significance  has  the  variation  of  the  thickness  of  the 
lead  weight?    Determine  the  upper  limit  of  thickness. 

(12)  Would  it  be  possible  to  determine  the  amount  of  work  accom- 
plished by  each  cilium?    By  each  stroke  of  a  cilium? 


CHAPTERII. 
THE  GENEKAL  PHYSIOLOGY  OF  MUSCLE  AND  NEEVE  TISSUE. 

VII.  ELECTRIC  APPARATUS  AND  UNITS  OF  MEASUREMENT. 

The  function  of  muscle  tissue  is  to  contract.  Muscles  contract 
only  in  response  to  stimuli.  Stimuli  may  act  upon  the  muscle  tissue 
— direct  stimulation;  or  upon  the  motor  nerve  which  supplies  the 
muscle — indirect  stimulation.  To  study  the  functions  of  muscles  and 
nerve  tissue  one  requires  to  have  at  command  various  methods  of 
stimulation.  It  is  usual  to  apply  mechanical,  thermal,  chemical  and 
electric  stimulation.  Experience  has  shown  that  of  all  these  means 
electricity  is  the  most  valuable,  because  it  is  subject  to  the  greatest 
number  of  variations  in  strength  and  in  method  of  application. 
Before  entering  upon  a  study  of  the  response  of  irritable  tissues  to 
electric  stimuli  it  is  essential  to  make  a  short  study  of  the  appliances 
used.  As  many  of  these  appliances  have  been  used  by  the  student 
in  the  physical  laboratory  it  will  be  taken  for  granted  that  he  is 
familiar  with  the  principles  involved  in  their  use. 

1.  Appliances.  Two  Daniell  elements  or  cells;  wires;  contact  key; 
Du  Bois-Reymond  key;  mercury  key;  commutator;  10  per  cent, 
sulphuric  acid;  copper  sulphate,  saturated  solution;  mercury. 

2.  Experiments  and  Observations,  (a)  The  Daniell  Cell.  Note 
the  four  parts  of  the  cell.  Half-fill  the  outer  receptacle  of  the  cell 
with  the  saturated  copper  sulphate  solution.  Put  the  copper  plate 
into  the  cell;  half-fill  the  porous  cup  with  the  dilute  sulphuric  acid; 
lower  the  zinc  plate  carefully  into  the  cup.  The  plate  is  of  com- 
mercial zinc  with  its  various  impurities. 

(1)  Observe  the  vigorous  chemical  action  in  porous  cup.  Express 
the  reaction  in  symbols.  It  is  evident  that  the  zinc  will  be  quickly 
consumed  if  allowed  to  remain  in  the  acid,  and  this  will  be  the  case 
whether  or  not  the  cup  and  zinc  plate  be  made  a  part  of  an  electric 
cell,  and  whether  the  cell  be  acting  or  resting. 

(2)  The  amaUjamation  of  ilie  zinc.  (See  also  Appendix,  4.)  Lift 
the  zinc  plate  out  of  the  acid,  dip  it  into  the  mercury.  The  mercury 
adheres  to  the  zinc,  mingles  witii  the  surface  layer  of  zinc,  forming 
an  alloy;  with  a  brush  or  an  old  cloth  one  may  rub  the  mercury  over 
the  whole  surface  of  the  zinc  plate — the  zinc  is  amalgamated.  The 
impurities  of  the  zinc  do  not  enter  into  the  alloy.  In  this  way  only 
the  j>Mre  zinc  which  forms  a  part  of  the  alloy  is  presented  to  the 


38 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


acid.  Chemically  pure  zinc  is  acted  upon  very  slowly  by  10  per  cent, 
sulphuric  acid.  Join  a  wire  to  the  exposed  end  of  each  plate;  touch 
the  tongue  with  the  free  end  of  each  wire  separately;  touch  the 
tongue  with  both  wires  simultaneously.    Record  results. 

(3)  Place  the  porous  cup  with  the  zinc  plate  in  the  receptacle 
holding  CuSO^  with  the  copper  plate.  Touch  the  tongue  with  one 
wire,  then  with  the  other.  Touch  the  tongue  with  both  at  once. 
Bring  the  two  free  ends  of  the  wire  into  contact  with  the  binding 


Fig.  13 


Fig.  14 


The  pole  changer,  or  the  Pohl  commutator.    (For  description 

see  text.) 

posts  of  a  galvanoscope.  Note  results. 
Touch  the  ends  of  the  wires  together;  if 
the  conditions  are  favorable  a  minute  spark 
may  be  seen  on  touching  and  on  separating 
the  two  poles.  What  conclusions  are  to  be 
drawn  ? 

(4)  Define  element  or  cell  as  used  in  this 
connection.  Define  plate,  pole,  electrode. 
The  zinc  is  arbitrarily  taken  as  the  positive 
plate  and  the  copper  as  the  negative  plate. 
The  pole  which  is  attached  to  the  negative 
plate  is  the  positive  pole,  and  that  which 
is  attached  to  the  positive  plate  is  the  nega- 
tive pole.  The  positive  pole  or  electrode 
of  a  galvanic  cell  or  of  a  battery  is  called  the  anode,  while  the 
negative  pole  or  electrode  of  a  cell  or  of  a  battery  is  called  the 
cathode. 

(6)  Keys.  (1)  Study  and  describe  the  simple  contact  key  (Fig. 
25,  K)  and  the  Du  Bois-Reymond  key  (Fig.  13).  (2)  The  two  ways 
of  using  the  Du  Bois-Reymond  key  are  shown  in  the  figures :  first,  as 
a  contact  key  (Fig.  15);  second,  as  a  short-circuiting  key  (Fig.  16). 


The  Du  Bois-Reymond  key. 


GEXEEAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     39 

(c)  The  Pole  Changer  or  Commutator.  ]\lost  convenient  for  the 
physiological  laboratory  is  Pohl's  commutator  (Fig.  14).  This  in- 
strument may  be  used  for  the  following  purposes: 

Fig.  15 


Fig.  16 


Fig.  17 


Fig.  18 


Fig.  19 


d)  To  change  the  direction  of  the  current.  Set  up  apparatus 
with  cross-bars  in  place  as  shown  in  Fig.  17.  Which  is  the  anode 
when  the  l)ridge  is  turned  toward  a  bf  Which  is  the  anode  when 
the  bridge  is  turned  toward  c  df 


40  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

(2)  To  change  the  course  of  the  current.  Set  up  apparatus  with 
cross-bars  removed  as  shown  in  Fig.  18.  What  course  will  the 
current  take  when  the  bridge  is  turned  toward  a  hf  What  course 
when  the  bridge  is  turned  toward  c  df 

(3)  Pohl's  commutator  may  be  used  as  a  simple  mercury  key 
(Fig.  19).  Is  the  current  open  or  closed  when  the  commutator 
bridge  is  turned  toward  af  How  may  the  current  be  opened  or 
broken? 

(d)  Work  Done  by  the  Electric  Cell.  The  experiments  performed 
show  that  the  galvanic  cell  may,  under  proper  conditions,  liberate 
energy.  This  energy  is  called  electricity.  But  the  immediate  source 
of  the  particular  electric  energy  liberated  in  the  foregoing  experiments 
is  the  latent  chemical  energy  represented  in  the  plates  and  liquids 
of  the  cell. 

Under  the  conditions  produced  in  the  working  galvanic  cell  the 
latent  chemical  energy  is  transformed,  and  at  the  same  time  liberated 
as  electric  energy.  This  liberated  electric  energy  may  make  itself 
manifest  in  the  contact  spark,  in  moving  the  galvanoscope  needle, 
or  in  lifting  the  armature  of  a  magnet.  In  the  last  case  mentioned 
it  would  not  be  difficult  to  determine  the  amount  of  work  done, 
though  it  might  be  somewhat  difficult  to  determine  the  amount  of 
work  which  a  cell  is  capable  of  performing  in  a  given  time.  If  one 
were  to  weigh  the  copper  plate  before  and  after  using  the  cell,  one 
would  find  that  it  had  increased  in  weight.  This  increase  in  weight 
is  an  index  of  the  amount  of  chemical  action  in  the  cell — of  the  latent 
chemical  energy  which  has  been  transformed  into  electric  energy. 

The  amount  of  electrolysis  must  be,  then,  an  index  of  the  amount 
of  current  that  is  afforded  by  a  cell  or  battery.  For  example,  if 
the  negative  pole  of  a  cell  be  attached  to  a  silver  or  platinum  cup 
containing  pure  nitrate  of  silver,  and  the  positive  pole  be  attached 
to  a  piece  of  pure  silver  which  is  immersed  in  the  silver  nitrate  solu- 
tion, it  will  be  found  that  one  ampere  of  current  will  uniformly 
deposit  0.001118  gm.  of.  silver  upon  the  cup  in  one  second  of  time. 
This  brings  us  to  the  question  of  the  units  of  electric  measurements. 

(e)  Electric  Units.     The   electric   energy  available   at  any  point 

in  a  circuit — i.e.,  the  current,  as  it  is  called — is,  according  to  Ohm's 

law,  equal  to  the  liberated  energy — the  electromotive  force — divided 

by  the  total  resistance  of  the  circuit.     This  is  expressed  in  Ohm's 

»         ,      ^_E.M.F.-  E     ^   .    . 

lormula,  G  —  — ^ c  =  ^.   It  is  impossible  for  the  physicist  to 

make  any  progress  in  the  study  of  electric  energy  without  arbitrarily 
assuming  units  of  measurement  for  current,  for  electromotive  force, 
and  for  resistance. 

(1)  Current  is  measured  in  amperes.  A  current  of  1  ampere  deposits 
upon  the  negative  electrode  of  a  galvanic  cell  or  battery  is  0.001118 
gm.  of  silver  per  second,  or  4.025  gm.  per  hour.    (See  above.) 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     41 

A  concrete  idea  of  the  ampere  may  be  gained  from  the  fact  that 
the  small-sized  Daniell  cell  produces  a  current  of  about  \  ampere 
when  the  external  resistance  is  reduced  to  a  minimum. 

(2)  Resistance  is  measured  in  ohms.  An  ohm  is  that  amount  of 
resistance  opposed  to  the  transmission  of  electric  energy  by  a 
column  of  mercury  1  sq.  mm.  in  cross-section  and  106.3  cm.  in 
length.  For  general  purposes  an  ohm  resistance  is  that  of  a  pure 
silver  wire  1  mm.  in  diameter  and  1  metre  in  length. 

(3)  Electromotive  force  is  measured  in  volts. 

A  volt  is  that  amount  of  electric  energy  which  will  produce  1 
ampere  of  current  after  overcoming  1  ohm  of  resistance. 

"The  ohm,  the  ampere,  and  the  volt  are  thus  closely  related, 
and  if  any  two  of  them  be  known  with  reference  to  any  particular 
electric  circuit  or  portion  of  a  circuit  the  value  of  a  third  may  be 

readily  inferred"  (Daniell) .    For  if  C  =  ^,  then  E=CXR  a^nd  R=^. 

The   same    relations    may   be   expressed   thus:    1    ampere    current 

1  volt  E.  M.  F.  ^  ^         1  volt 

==  — , . ,  or  1  ampere  =_ — - — . 

1  ohm  resistance  1  ohm 

Therefore  (1 )  volts  =  amperes  X  ohms ;  (2)  amperes  =  volts  -^  ohms ; 
(3)  ohms  =  volts -7- amperes. 

The  small  Daniell  cell  has  about  1  volt  E.  M.  F.  and  4  ohms 
resistance ;  the  current  from  such  a  cell  is  then  equal  to  approximately 
J  ampere. 

There  are  niunerous  other  units  of  measurement  used  by  physicists 
and  electricians,  but  for  our  purpose  it  is  not  necessary  to  review  these 
more  specialized  points. 

VIII.  BATTERIES. 

A  Vjattery  is  a  group  of  two  or  more  elements  or  cells  arranged 
to  produce  increased  or  modified  effect.  If  one  wishes  to  use  a 
stronger  current  than  that  afforded  by  one  cell,  his  first  thought  is 
to  increase  the  number  of  cells,  or  to  procure  a  larger  cell.  Experi- 
mentation will  show  him  that  it  is  not  a  matter  of  indifference  which 
of  these  courses  to  pursue.  In  the  first  place,  if  he  attempts  to  satisfy 
the  conditions  he  will  find  that  to  increase  the  size  of  a  cell  increases 
the  current  only  when  the  external  resistance  is  relatively  small, 
and,  furthermore,  there  are  practical  limitations  to  the  size  of  a  cell, 
and  these  may  be  much  within  the  requirement  which  the  cell  must 
satisfy.  It  becomes  apparent,  then,  that  he  who  would  use  electric 
energy  beyond  the  most  limited  field  must  resort  to  a  battery  com- 
posed of  a  number  of  cells.  The  problem  which  first  confronts  him 
is,  Hf>\v  shall  these  cells  be  arranged? 

1.  Appliances.  Six  Daniell  cells;  wires;  galvanoscope  (Fig.  24), 
composed  of  a  simple  magnetic  needle  mounted  over  a  circle  divided 


42 


EXPERIMENTAL  OENEBAL  PHYSIOLOGY 


into  degrees;  rheostat  or  resistance  box,  representing  at  least  100 
ohms. 

2.  Experiments  and  Observations.  (1)  (a)  Join  up  apparatus  as 
shown  in  Fig.  20.  With  the  plugs  all  fixed  in  the  rheostat — i.  e., 
with  no  resistance  except  that  of  the  wires  and  battery,  and  the 
indicator  needle  at  0° — open  the  key  and  then  observe  the  angle  at 
which  the  needle  comes  to  rest. 


Fig.  20 


(6)  Remove  from  the  rheostat  the  plug  which  will  throw  into  the 
circuit  an  extra  resistance  of  10  ohms.  Allow  the  needle  to  come  to 
rest  and  note  angle. 

(c)  Remove  from  the  rheostat  plugs  which  will  represent  in  the 
aggregate  100  ohms  extra  resistance.  Note  angle  of  indicator  as 
before. 

(2)  Join  up  two  cells  in  multiple  arc,  as  shown  in  Fig.  21.  That 
is,  join  both  copper  plates  to  one  copper  wire  and  both  zinc 
plates  to  another.  These  wires  are  to  be  carried  to  key,  rheostat, 
and  galvanoscope,  as  shown  in  Fig.  20. 

(a)  Note  angle  of  needle  with  no  extra  resistance. 

(h)  Note  angle  with  10  ohms  extra  resistance. 

(c)  Note  angle  with  100  ohms  extra  resistance. 


Fig.  21 


(3)  Join  up  four  cells  in  multiple  arc  or  "abreast,"  and  repeat 
the  observation  of  angle  at  the  three  resistances  as  above. 

(4)  Join  up  six  cells  in  multiple  arc  and  repeat  observations  with 
0  ohm,  10  ohms,  and  100  ohms  resistance. 

(5)  Join  up  two  cells  in  series,  as  shown  in  Fig.  22.  That 
is,  join  the  copper  of  the  first  cell  to  the  zinc  of  the  second.  The 
first  cell  will  have  a  zinc  uncoupled  and  the  second  will  have 
a  copper  plate  uncoupled.  These  two  uncoupled  terminal  plates 
of  the  battery  are  the  ones  from  which  to  lead  off  the  wires  to  the 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     43 

other  apparatus,  which  should  be  arranged  as  shown  in  Fig,  20. 
Repeat  the  observations  on  the  angle  of  deviation  of  the  needle  using 
the  0  ohm,  10  ohms,  and  100  ohms  resistance  as  above. 

(6)  Join  up  four  cells  tandem  or  in  series,  and  repeat  the  three 
observations. 

(7)  Join  up  six  cells  in  series  and  repeat  observations. 

(8)  Tabulate  results  and  draw  conclusions: 

1.  There  is  a  marked  difference  in  the  results  of  the  two  methods. 

2.  With  low  external  or  circuit  resistance  the  current  is  indicated 
by  the  angle  at  which  the  galvanoscope  needle  stood  increased  with 
an  increase  in  the  number  of  cells  joined  multiple  arc  or  abreast. 


Fig.  22 


3.  With  high  external  resistance  the  strength  of  the  current  does 
not  seem  to  be  essentially  increased  by  increasing  the  number  of 
cells  joined  up  abreast. 

4.  With  low  external  resistance  the  strength  of  the  current  is  not 
increased  by  adding  cells  in  series. 

5.  With  high  external  resistance  the  strength  of  current  increases 
with  an  increase  in  the  number  of  cells  joined  up  in  series  or  tandem. 


IX.  METHODS  OF  VARYING  THE  STRENGTH  OF  CURRENT. 

It  has  already  been  shown  that  the  strength  of  current  may  be 
varied  by  increasing  the  numl^er  of  cells  or  by  changing  their  arrange- 
ment in  the  battery.  This  method  is  indispensable,  but  it  has  its 
limitations.  If  one  has  a  small  cell  and  wishes  to  decrease  the  current, 
he  must  have  a  recourse  to  another  method. 

E 
From  the  formula  C=      it  is  evident  that  one  may  decrease  the 
R 

current  by  increasing  the  resistance. 

{a)  The  Rheostat. 

1.  Appliances.  Resistance  l)ox  or  rheostat;  1  cell;  5  wires; 
galvanoscope  or  galvanoinctci'. 

2.  Experiments  and  Observations.  (I)  Set  up  tiie  apparatus  as 
.shown  in  Fig.  20. 


44 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


(1)  With  plugs  all  fixed  in  rheostat,  needle  of  galvanoscope  at  0°, 
close  key  and  note  angle  of  deviation. 

(2)  Remove  the  plug,  which  will  throw  into  circuit  the  lowest 
resistance  contained  in  the  rheostat.     Note  the  angle. 

(3)  Add  to  the  above  resistance  the  smallest  possible  increment 
and  note  angle. 

(4)  Proceed  in  this  way,  tabulating  results. 

(5)  Conclusions. 


Fig.  23 


(II)  Another  method  of  using  the  rheostat.  The  rheostat  may 
be  used  in  short  circuit,  as  shown  in  Fig.  23.  From  this  arrange- 
ment of  the  apparatus  it  is  apparent  that  when  all  the  plugs  are 
in  place  the  current  will  be  short-circuited  by  the  rheostat.  If  the 
resistance  of  that  part  of  the  circuit  leading  to  the  galvanoscope 
— the  long  circuit — be    considerable,  the   long-circuit  current  will 


Fig.  24 


Galvanoscope,  composed  of  a  single  magnetic  needle  mounted  over  a  graduated  circle.  The 
two  heavy  copper  wires  which  encircle  the  compass  offer  slight  resistance  to  the  passage  of  the 
electric  current. 


probably  not  be  sufficient  to  cause  any  deviation  of  the  galvanoscope 
needle;  for  the  current  varies  inversely  as  the  resistance  (Coo  -i),  and 

if  the  resistance  of  the  short  circuit  {R')  equals  zero,  then  the  current 
of  the  long  circuit  (C)  will  be  incomparably  less  than  the  current  of 

the  short  circuit  {C')—i.e.,  C:C'::  i;!  ,  or  C:C'::  R':R;   therefore, 


if  i?'  =  0,  C  must  equal  0. 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     45 

Suppose  that  the  resistance  of  the  galvanometer  circuit  {R')  be 
only  10  ohms,  and  suppose  we  remove  from  the  rheostat  the  plug 
that  represented  0.1  ohm  resistance,  then  one-hundredth  of  the 
current  will  pass  through  the  galvanometer.  If  we  make  the  resist- 
ance in  the  short  circuit  0.2  ohm,  then  one-fiftieth  of  the  current 
will  flow  through  the  long  circuit. 

Problem.  In  this  way  we  may  increase  the  galvanometer  current 
step  by  step  until  the  maximum  is  reached. 

What  is  the  maximum  current  to  be  derived  when  the  resistance 
in  the  galvanometer  circuit  (R')  equals  10  ohms,  the  maximum 
resistance  of  the  rheostat  (R)  equals  100  ohms,  external  resistance 
in  circuit  between  cell  and  rheostat  (r)  equals  1  ohm,  E.  M.  F.= 
1  volt,  and  internal  resistance  of  cell  4  ohms? 


(6)  The  Simple  Rheocord. 

Besides  the  methods  alreadv  used  for  varving  the  strength  of  the 
current  one  may  use  the  derived  current. 

The  simple  rheocord  (Fig.  25)  may  be  used  for  this  purpose. 

Fig.  25 


Rheocord  with  contact  key. 

1.  Appliances.  One  or  more  cells;  simple  rheocord;  five  wires; 
galvaiioinctcr. 

2.  Experiments  and  Observations.  (1)  Set  up  the  apparatus 
as  shown  in  Fig.  25.  From  the  figure  we  see  that  from  the  cell 
to  post  A,  thence  through  the  German-silver  wire  to  post  B  and 
back  to  tlie  cell  makes  a  complete  circuit.     Having  reached  the 


46  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

metallic  slider  {S)  the  circuit  has  two  paths  presented:  1st,  from  S 
direct  to  B;  2d,  from  S  through  G  and  back  to  B.  The  total  current 
is  divided  into  two  parts :  C,  which  passes  along  the  wire  from  S  to  B, 
and  C ,  the  derived  circuit  which  passes  through  the  galvanometer. 
Suppose  the  resistance  to  the  last-named  current  is  R  and  that  to 
the  direct  current  is  R,  the  relative  strength  of  these  two  currents 
is  expressed  in  the  following  proportion:     C':C  :  :  R :  R' . 

But  the  resistance  of  the  German-silver  wire  may  be  conveniently- 
divided  into  100  equal  parts  (100  r). 

If  the  sHder  be  placed  at  any  position  along  the  wire,  say  at  X  cm. 
from  the  end,  then  the  formula  would  be  C :  C :  :  xr :  R' . 

Suppose  that  R=l  ohm  (r  =  0.01  ohm);   R'  =  2  ohms   and  a;=0; 

XT 

i.  e.,  suppose  the  slider  to  hard  up  to  B,  then  C'=  ~C^0.     This 

makes  it  clear  that  when  the  slide  is  in  the  zero  position  there  will 
be  no  current  passing  through  the  galvanoscope. 

(2)  What  is  the  relative  strength  of  the  two  currents  when  x=10? 

(3)  What  is  the  relative  strength  of  the  two  currents  when  a;  =50? 

(4)  What  is  the  relation  of  C  to  C  when  a;  =99? 

(5)  What  is  the  relation  of  C  to  C  when  a;  =100? 

From  this  course  of  reasoning  it  is  evident  that  in  the  simple 
rheocord  we  have  an  instrument  with  which  we  can  vary  a  derived 
current  from  zero  to  a  maximum.  Just  what  the  value  of  this  derived 
current  will  be  will  depend  upon  the  voltage  of  the  cell  or  battery 
and  the  total  resistance  to  be  overcome,  as  well  as  upon  the  distribu- 
tion of  that  resistance. 

(6)  Verify  the  theory  just  developed,  making  a  table  of  galvano- 
scope readings. 

X.  MUSCLE-NERVE  PREPARATION. 

(a)  The  Classic  Muscle-nerve  Preparation. 

1.  Appliances.  Frog  board  and  pins;  operating  case;  glass  nerve 
hooks,  like  Fig.  28,  A,  made  as  follows:  take  a  10  cm.  piece  of 
glass  rod,  heat  and  draw  in  center  to  about  IJ  mm.  diameter;  cool, 
cut  in  two,  heat  the  points  to  smooth  them,  and  bend  the  end  over 
to  form  the  hook. 

Simple  myograph  or  muscle  lever  (Fig.  26).  Watch-glass  with  salt 
crystals;  20  cm.  of  thick  copper  wire. 

2.  Preparation.  Pith  a  frog  and  fix  to  frog  board,  with  dorsum 
up.  It  will  be  taken  for  granted  that  the  student  is  familiar  with  the 
anatomy  of  the  frog's  leg  and  thigh.  The  accompanying  cut  (Fig.. 
27)  may  serve  to  refresh  the  memory. 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     47 

Fig.  26 


The  simple  myograph  :   C,  femur  clamp ;  S,  glass  slide  on  which  to  rest  the  nerve  ;  i/, [tendon 
hook  of  myograph  lever  ;  T,  tracing  point  of  myograph  lever. 


Fig.  27J 


Sh'jwiriK  muKcuIature  of  the  frog'H  thigh  ami  leg:  A,  ventral  aspect;  //,  tlorsal  aspect. 


48 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


3.  Operation.  To  make  a  gastrocnemius  "muscle-nerve  prep- 
aration." 

(1)  Make,  with  scissors,  a  circular  cutaneous  incision  around  the 
tarsus,  corresponding  with  the  lower  end  of  cut  B.  Make  a  longi- 
tudinal cutaneous  incision,  beginning  at  the  margin  of  the  circular 
incision  where  it  crosses  the  external  aspect  of  the  tarsus,  carry  it 
along  the  tibia,  along  the  course  of  the  biceps  femoris  muscle,  over 
the  pyriformis  to  the  posterior  end  of  the  urostyle,  along  the  whole 
extent  of  the  urostyle.  From  the  posterior  end  of  the  urostyle  make 
an  incision  posteriorly  and  ventrally,  for  1  cm.  or  2  cm.  Grasp  the 
free  margin  of  the  skin  at  the  point  of  the  circular  incision  and  with 
a  quick  traction  toward  the  head  of  the  frog  the  skin  will  be  removed 
from  the  whole  field  of  operation. 


Fig.  28 


A,  a  glass  nerve  hook;  B,  the  classic  muscle-nerve  preparation. 

(2)  Pass  a  point  of  the  fine  scissors  under  the  glistening  tendon 
of  the  biceps  femoris  where  it  is  inserted  into  the  tibia,  taking  care 
not  to  injure  any  of  the  neighboring  tissues.  Sever  the  tendon. 
Grasp  its  free  end;  lift  the  biceps  up,  carefully  cutting  the  delicate 
connective  tissue  which  joins  it  to  neighboring  structures;  sever 
its  heads.  The  removal  of  the  biceps  and  a  separation  of  the  cleft 
which  the  biceps  occupied  reveals  three  bloodvessels  and  the  large 
trunk  of  the  sciatic  nerve.  Which  of  the  bloodvessels  is  the  sciatic 
artery?  Which  is  the  sciatic  vein?  Which  is  the  femoral  vein? 
_  (3)  Grasp  and  lift  up  the  posterior  end  of  the  urostyle,  sever  the 
iliococcygeal  muscles,  remove  the  urostyle. 

The  sciatic  plexuses  formed  by  the  seventh,  eighth,  and  ninth 
pairs  of  spinal  nerves  will  be  revealed. 

(4)  Pass  a  glass  nerve  hook  under  the  sciatic  nerve;  gently  lift  it 
up,  severing,  with  the  scissors,  the  connective  tissue.  The  pyriformis 
muscle  must  also  be  divided.    The  whole  length  of  the  sciatic  nerve 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     49 

may  thus  be  readily  dissected  out.  Care  should  be  taken  not  to 
stretch,  pinch,  or  cut  the  nerve  during  this  process.  Lay  the  nerve 
upon  the  gastrocnemius  muscle. 

(5)  Grasp  the  triceps  femoris  muscle,  pass  a  blade  of  the  scissors 
under  its  tendon;  sever,  and  remove  the  whole  mass  of  muscles 
anterior  to  the  femur.  In  a  similar  manner  remove  the  muscles 
posterior  to  the  femur. 

(6)  Grasp  the  tendo  Achillis,  sever  it  low  down  where  it  passes 
over  the  calcaneum,  lift  up  the  gastrocnemius  and  sever  the  tibia 
and  its  associated  muscles  as  near  the  knee-joint  as  possible. 

(7)  Sever  the  femur  at  the  juncture  of  its  middle  and  upper  thirds. 
The  finished  preparation  has  the  characteristics  shown  in  Fig.  28. 
A  segment  of  the  vertebral  column  may  or  may  not  be  left  on. 

(6)  The  Indirect  Stimulation  of  the  Gastrocnemius. 

4.  Observations.  To  mount  the  muscle-nerve  preparation  in  the 
myograph.  Fix  the  femur  in  the  clamp  (Fig.  26,  C) ;  place  a  piece 
of  filter  paper,  wet  with  normal  saline  solution,  upon  the  glass  nerve- 
support  (S) ;  lay  the  nerve  upon  the  support,  make  a  longitudinal 
slit  in  the  tendo  Achillis,  pass  the  hook  of  the  muscle  lever  through 
the  slit,  and  so  adjust  the  height  of  the  clamp  as  to  bring  the  lever 
into  a  horizontal  position. 

(a)  Mechanical  Stimulation.  (1)  Snip  off  with  the  scissors  the 
central  end  of  the  sciatic  nerve.  If  the  muscle  instantly  contracts, 
thereby  lifting  the  lever,  the  observer  will  know  that  his  preparation 
is  successful.  If  it  does  not  respond  to  the  first  stimulation  it  may 
to  a  second  or  subsequent  one.  If  it  responds  to  later  stimuli,  but 
not  to  the  first  ones,  one  may  conclude  that  in  making  the  prepara- 
tion a  portion  of  the  central  end  of  the  nerve  was  killed. 

(2)  What  may  one  conclude  if  the  muscle  responds  to  stimuli 
applied  to  a  central  end  of  the  sciatic  nerve,  but  later  fails  to  respond 
to  stimuli  applied  farther  along  the  course  of  the  nerve — i.  e.,  nearer 
the  muscle? 

(b)  Thermal  Stimulation.  Make  and  mount  a  fresh  preparation. 
Heat  the  copper  wire  in  a  gas  flame  and  touch  the  end  of  the  nerve 
with  the  hot  wire.  If  the  preparation  has  been  successful  the  muscle 
will  respond  by  a  contraction.  If  the  preparation  is  a  good  one, 
.save  at  least  two-thirds  of  the  nerve  for  the  subsequent  experiment. 

(c)  Chemical  Stimulation.  Cut  off  the  part  of  the  nerve  which  is 
(h'iul  and  lay  the  central  end  of  the  still  functional  nerve  in  a  saturated 
.solution  of  common  salt.    Await  results.     Record  all  results. 

(d)  Electric  Stimulation.  While  in  the  operation  of  making  a 
gastrocnemius  prej>aration  after  the  sciatic  nerve  has  been  freed  from 
the  other  structures  in  the  thigh,  slip  the  glass  nerve  hook  under  it 
.so  that  the  handle  of  the  nerve  hook  will  hold  the  nerve  away  from 

4 


50 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


the  other  tissues.  Press  the  end  of  a  copper  wire  against  the  muscles 
of  the  thigh;  touch  the  silver  probe  to  the  sciatic  nerve,  then  to  the 
copper  wire,  first  separately  then  simultaneously. 

Vary  the  experiment  by  using  other  combinations:  silver  and 
steel,  copper  and  steel,  etc.  Note  briefly  the  original  observations 
of  Galvani.  Are  the  observations  just  made  different  in  any  essential 
respect  from  the  observation  which  led  to  the  discovery  of  what  we 
call  galvanic  electricity? 


XI.  ELECTRIC  STIMULATION  AND  THE  MYOGRAM. 

The  simplest  work  in  the  field  of  electro-physiology  is  that  which 
involves  the  use  of  the  induction  shock  as  a  stimulus  and  the  use 
of  a  myograph  and  kymograph  to  record  the  result  of  the  stimulus. 


The  inductorium. 


1.  Appliances.  Inductorium;  myograph;  kymograph;  frog;  oper- 
ating case;  glass  hook;  dry  cell;  contact  key  with  three  wires;  shielded 
electrode  with  two  wires;  normal  saline  solution. 

2.  Apparatus,  (a)  The  Frog-board  Myograph.  The  frog-board 
myograph  is  a  new  form  of  myograph,  so  constructed  as  to  permit  all 
experiments  usually  performed  on  the  gastrocnemius-sciatic  prepara- 
tion without  exposing  the  active  tissues  to  the  atmosphere  or  dis- 
turbing the  blood  supply.  The  instrument  is  constructed  as  follows: 
An  oaken  base  about  one-fourth  of  an  inch  in  thickness  supports 
a  cork  plate  of   equal  thickness;  the  cork  plate  presents  a  surface 

"about  10  cm.  by  25  cm.  (Fig.  31).  The  lever  holder  at  the  end 
of  the  plate  is  constructed  of  thin  sheet  steel  and  slips  from  side 
to  side  in  order  to  bring  it  opposite  either  leg  of  the  frog. 

The  distance  from  the  axis  of  the  elbow  lever  to  the  thread-eye 
is  the  same  as  that  to  the  weight;  therefore,  the  weight  hfted  by  the 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     51 

muscle  is  the  actual  -weight  hung  upon  the  weight  link.  When  the 
lever  passes  a  little  below  the  horizontal  position  it  comes  in  contact 
with  the  rest.  This  rest  can  be  used  in  "after-loading"  a  muscle. 
For  further  description  of  the  instrument  see  Fig.  31  and  its  legend. 

Fig.  30 


The  Neef  hammer. 


In  the  use  of  the  frog-board  myograph  one  proceeds  as  follows: 
The  frog  is  pithed  and  pinned,  dorsum  up,  on  the  cork  plate,  with 
the  feet  at  the  lever  end.  The  tendo  Achillis  is  exposed  and  loosened 
from  the  tarsal  ligaments;  the  tendon  hook  jV  is  passed  through 
the  tendon  and  the  length  of  the  thread  adjusted  at  C.  The  skin 
on  the  thigh  is  opened  to  the  extent  of  2  cm.  and  the  biceps  femoris 
muscle   removed,   the   sciatic   nerve   carefully   separated   from   the 


Fig.  31 


Frog-board  myograph  :  S,  the  shaft  which  is  clamped  to  the  upright  stand ;  B,  the  oaken 
base;  C Pt,  the  cork  f>late  to  which  the  frog  is  fixed  ;  A,  the  lever  axis  and  slide  lever  holder; 
IK,  the  weight;  L,  the  light  lever,  about  20  cm.  in  length  ;  N,  the  tendon  hook  which  is  joined 
through  the  thread  T,  which  passed  through  the  eye  and  under  spring  the  catch  C;  R,  the  lever 
re»t. 

sciatic  artery  and  placed  on  the  insulated  electrodes.  Stimulation 
may  be  made  from  time  to  time  for  a  period  of  several  hours  before 
the  preparation  becomes  exhausted. 

(h)  The  Inductorium.  This  instrument  consists  of  two  spools  of 
wire:  a  prirnari^  circuit  of   few  turns  of  coarse  wire  and  a  secondary 


52 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


circuit  of  many  turns  of  fine  wire.  It  will  be  assumed  that  the 
principle  of  the  inductorium  is  familiar  to  the  student  through  his 
previous  work  in  physics.     (See  Figs.  29  and  30.) 

The  inductorium  used  in  the  physiological  laboratory  is  provided 
with  a  vibrating  (Neef)  hammer  which  makes  and  breaks  the  current 
with  each  double  vibration  of  the  hammer,  the  vibration  being 
due  to  the  reciprocal  action  of  an  electromagnet  and  a  spring.  The 
instrument  must  also  be  provided  with  a  means  for  either  cutting  the 
hammer  out  of  the  primary  circuit  or  stopping  the  vibration  of 
the  hammer.  The  secondary  coil  or  induction  circuit  must  be  pro- 
vided with  a  short-circuiting  key,  either  as  a  part  of  the  inductorium 
or  as  an  extra  appliance. 


Fig.  32 


Fig.  33 


The  kymograph. 


Drum  support  for  use  in  smoking  the  kymograph  drums. 


The  secondary  coil  is  movable  and  may  be  moved  up  until  it  covers 
the  primary  coil  or  moved  out  along  a  slide.  Some  instruments  are 
provided  with  a  long  base,  permitting  the  secondary  coil  to  be  moved 
to  a  considerable  distance  from  the  primary  coil,  while  others  are 
provided  with  a  short  base  and  a  pivot,  allowing  the  secondary  coil 
to  be  turned  through  an  angle  of  90  degrees  after  it  has  been  drawn 
back  free  from  the  primary  coil.  Either  arrangement  allows  one 
to  decrease  at  will  the  strength  of  the  induction  shocks. 

(c)  The  Kymograph  (Fig.  32).  This  instrument  is  the  most 
important  one  in  any  physiological  laboratory,  because  with  its  help 
graphic  records  of  all  movements  of  tissues  and  organs  and  of  all 
pressure  changes  may  be  made.     The  kymograph  or  wave-writer  is 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     53 

thus  used  in  nearly  all  work  in  the  neuromuscular  system,  the 
circulatory  system,  and  the  respiratory  system. 

The  instrument  consists  of  a  cylinder  or  drum  kept  in  rotation  by 
clock-work.  The  rate  of  the  rotation  is  usually  governed  by  fans 
of  varying  sizes,  also  by  adjustments  of  the  propelling  mechanism. 

To  prepare  the  kymograph  for  work,  remove  the  cylinder,  stretch 
a  sheet  of  prepared  glazed  paper  tightly  upon  the  surface  and  place 
it  upon  such  a  stand  as  that  shown  in  Fig.  33.  Set  the  drum  to 
rotating  and  bring  a  gas  flame  or  preferably  a  triple  flame  under  the 
drum.  In  a  few  moments  it  will  be  evenly  covered  with  a  film  of 
carbon,  which  is  as  sensitive  to  touch  as  a  photographer's  plate  is 
to  light. 

To  fix  the  carbon  tracings  and  make  the  record  a  permanent  one 
see  directions  in  Appendix,  8. 

3.  Experiments  and  Observations.  Pith  a  frog;  mount  it  upon 
the  frog-boartl  myograph  as  directed  above.  Prepare  the  kymograph 
for  receiving  a  tracing  and  adjust  it  for  slowest  rotation.  Adjust 
the  myograph  so  that  its  tracing  lever  stands  horizontal  and  tangent 
to  the  drum  with  the  tracing  point  lightly  touching  the  side  of  the 
drum.  Set  up  the  electric  apparatus  with  one  dry  cell  or  one 
Daniell  cell  so  joined  in  the  primary  circuit  as  to  avoid  the  action 
of  the  vibrating  hammer.  Use  a  contact  key  in  the  primary  circuit 
and  a  short-circuiting  key  in  the  secondary  circuit. 

(1)  Determine  the  stimulus  of  liminal  intensity  by  moving  the 
secondary  coil  to  position  of  minimum  strength;  then,  while  slowly 
"making  and  breaking"  the  current  in  the  primary  circuit,  move 
the  secondary  coil  up  until  the  strength  of  the  induction  shock  is 
sufficient  to  cause  a  contraction  of  the  muscle.  The  weakest  shock 
which  will  cause  a  contraction  is  the  stimulus  of  liminal  in- 
tensity sought.  Note  that  this  occurs  on  the  break  of  the  primary 
circuit. 

(2)  Determine  the  stimulus  of  optimum  intensity  by  starting  the 
kymograph  to  rotating  slowly;  meanwhile  make  and  break  the 
primary  circuit  while  continuing  to  move  the  secondary  coil  from 
the  position  of  liminal  intensity  toward  the  position  of  maximum 
intensity.  The  myograph  will  trace  a  series  of  myograms  with  the 
rise  and  fall  of  the  lever,  when  the  muscle  contracts  and  relaxes. 
The  tracings  will  present  a  series  of  sharp-pointed  waves  varying 
in  height,  showing  the  varying  extent  of  contraction.  At  first  all  the 
contractions  occur  on  break  of  primary  circuit,  then  on  both  break 
and  make  of  the  primary  circuit.  As  the  secondary  coil  is  moved 
toward  the  maximum  position  the  myograms  become  higher  and 
higher,  finally  reaching  a  maximum  height  which  is  not  exceeded, 
however  strong  the  stimulus  is  made. 

The  stimulus  of  optimum  intensity  is  the  weakest  stimulus  which 
v:ill  produce  the  maximum  contraction. 


54  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

The  increase  of  the  strength  of  stimulus  beyond  the  optimum  will 
only  fatigue  the  muscle  and  nerve  through  overstimulation,  without 
producing  greater  contractions. 

4.  Observations.  (1)  Take  tracings  of  the  contractions  produced 
by  a  series  of  "make-induction  shocks"  applied  indirectly — i.  e., 
to  the  nerve.  The  "make-induction  shock"  is  obtained  as 
follows : 

(a)  With  primary  circuit  not  interrupted  by  the  Neef  hammer,  but 
closed  and  opened  by  the  contact  key,  open  the  short-circuiting  key 
of  the  induced  circuit. 

(6)  Close  the  contact  key  of  the  primary  circuit  and  make  induc- 
tion shock — i.  e.,  a  shock  in  the  induced  circuit  caused  by  a  closure 
of  the  battery  circuit  will  stimulate  the  preparation. 

(c)  Close  the  short-circuiting  key  in  the  secondary  circuit. 

(d)  Open  or  break  the  primary  circuit.  An  induced  break  shock 
occurs  in  the  secondary  circuit,  but  it  is  short-circuited  by  the  closed 
Du  Bois-Reymond  key.  If  while  the  drum  rotates  one  makes,  in 
close  succession,  the  changes  above  indicated — a-b-c-d,  a-b-c-d,  etc. — 
there  will  be  produced  a  series  of  contractions,  all  the  result  of 
stimulation  by  make-induction  shocks. 

(2)  Take  a  tracing  of  the  contractions  resulting  from  a  series 
indirectly  applied — break-induction  shocks. 

(3)  By  leaving  the  short-circuiting  key  open  one  may  get  a  series 
of  contractions  due  to  alternating  make-induction  shocks  and  break- 
induction  shocks.  Let  these  be  recorded  in  pairs  upon  the  kymo- 
graph. 


XII.  THE  TYPICAL  MYOGRAM,  COMBINED  MYOGRAMS, 
AND  TETANUS. 

1.  Appliances.  Inductorium;  Daniell  cell  or  dry  cell;  kymograph; 
myograph;  electrodes;  keys;  wires. 

2.  Preparation.  Pith  a  frog,  make  muscle-nerve  preparation; 
mount  it  on  myograph,  prepare  kymograph  for  tracing,  and  adjust 
for  fastest  rotation;  set  up  electric  apparatus  for  a  series  of  make- 
induction  shocks  or  break-induction  shocks. 

3.  Experiments  and  Observations.  (1)  Start  the  kymograph 
drum  to  rotating.  When  it  has  reached  the  maximum  speed,  stimu- 
late the  preparation  with  a  break-induction  shock.  The  lever  point 
should  trace  upon  the  drum  a  typical  myogram.  Repeat  the  experi- 
ment several  times  with  the  same  preparation.  Study  the  character- 
istics of  the  myogram. 

(2)  Trace  another  myogram  while  a  tuning  fork  is  tracing  hun- 
dredths of  seconds  upon  the  drum  and  while  the  instant  of  stimulating 
the  nerve  is  traced  upon  the  drum,  either  through  the  action  of  an 


GENERAL  PHYSIOLOG  Y  OF  MUSCLE  AXD  NERVE  TISSUE     55 

electromagnet  and  tracing  lever  or  through  a  tracing  lever  attached 
to  the  key  of  the  primary  circuit.  There  will  thus  be  three  tracings 
upon  the  drum:  (a)  the  myogram;  (b)  the  time  tracing;  (c)  the 
stimulus  tracing,  the  latter  showing  the  time  when  the  stimulus  is 
made.  Note  that  the  myograph  lever  does  not  rise  until  a  certain 
time  after  the  stimulus  is  given.  This  period  is  the  latent  period. 
What  is  the  length  of  the  latent  period? 

(3)  Trace  another  myogram,  but  as  the  lever  is  sinking  back 
toward  the  abscissa  stimulate  a  second  time.  Note  that  the  result 
is  a  double-crested  myogram  and  that  the  second  is  higher  than 
the  first. 

(4)  Trace  another  myogram  resulting  from  a  series  of  stimuli 
occurring,  in  rapid  succession,  if  possible  about  ten  times  per  second. 
Note  that  the  result  is  a  myogram  with  a  series  of  crests  and  that 
the  lever  does  not  fall  back  to  the  abscissa  between  the  successive 
stimuli.  Note  that  the  first  few  crests  are  progressively  higher  and 
higher.  This  phenomenon  is  called  the  "stair-case  series  of  con- 
tractions," and  is  usually  observed  when  a  muscle  is  given  a  series 
of  stimuli  after  a  period  of  rest. 

(5)  Vary  the  above  experiment  by  increasing  the  rapidity  of 
stimuli  to  20  per  second.  This  may  be  done  through  the  use  of 
a  toothed  wheel  as  a  key  in  the  primary  circuit,  or  through  modifica- 
tion of  the  Neef  hammer,  which  causes  it  to  vibrate  slowly.  Use 
medium  speed  of  kymograph.  Note  that  the  result  is  a  myogram 
with  a  serrated  crest,  the  serrations  indicating  the  result  of  the 
several  stimuli. 

(6)  Stimulate  with  a  series  of  induct  shocks  caused  by  the  rapid 
making  or  breaking  of  the  primary  circuit  through  the  vibration 
of  the  Neef  hammer.  Use  medium-speed  drum.  Note  that  this 
throws  the  muscle  into  a  condition  of  typical  tetanus. 

Trace  a  series  of  tetanus  curves,  each  lasting  about  three  or  four 
seconds. 

XIII.  THE   WORK  DONE  BY  A  MUSCLE. 

(a)  To  determine  the  amount  of  work  done  by  a  single  contraction. 
(h)  To  determine  the  total  amount  of  work  done  by  a  muscle,  (c) 
Reaction  changes  in  fatigued  muscles. 

1.  Appliances.  Same  as  Lesson  XII.;  also  50-gram  Aveight  and 
20-gram  or  .30-gram  weight. 

2.  Preparation.  Arrange  electric  apparatus  for  a  series  of 
break-induction  shocks. 

.J.  Operation.  Make  and  mount  a  gastrocnemius  preparation 
for  indirect  stimulation. 

4.  Observations,  rjjon  a  slow  di-um  record  in  close  order  a 
.series  of  break  contractions. 


56  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

(a)  To  determine  the  amount  of  work  done  by  a  single  contraction. 

(1)  What  weight  is  hfted? 

(2)  How  high  is  it  raised? 

(3)  What  is  the  ratio  between  the  height  of  the  curve  traced  by 
the  lever  and  the  height  through  which  the  weight  was  raised? 

(4)  Let  ]F=work  done. 

^= weight  hfted. 

/^=  height  of  curve  traced  by  lever. 
h=  constant   of   the   apparatus,    in   this   case   the   ratio 
between  the  lever  arms.     Then  W=k.  g.  h. 

(5)  Express  the  amount  of  work  in  ergs. 

(b)  To  determine  total  work  done. 

(6)  How  many  times  was  the  weight  lifted  before  the  muscle 
was  fatigued? 

(7)  Through  what  average  height  was  the  weight  lifted? 

(8)  Has  the  value  of  k  or  g  changed? 

(9)  Give  a  formula  for  total  height  (H^=). 

(10)  Give  a  formula  for  total  work  done  (W=). 

(11)  Express  in  ergs  the  total  work  done  by  the  muscle. 

(12)  In  the  fatigue  tracing,  did  the  lever  continue  throughout 
the  observation  to  fall  back  to  the  original  abscissa?  If  not,  describe 
the  general  changes  in  the  abscissa. 

(c)  Reaction  changes. 

(13)  Apply  a  piece  of  neutral  litmus  paper  to  the  fresh  muscle 
tissue  of  the  frog  from  which  your  specimen  was  taken.  Record 
result. 

(14)  Apply  a  piece  of  litmus  paper  to  a  fresh-cut  surface  of  the 
fatigued  muscle.     Record  results. 

(15)  What  is  the  reaction  of  a  muscle  of  a  frog  after  rigor  mortis 
has  been  established? 

(16)  What  is  the  reaction  of  fresh  urine? 

(d)  Secondary  fatigue  (Lagrange,  p.  60). 

(17)  Grind  a  fatigued  or  exhausted  muscle  in  a  mortar  and  extract 
with  normal  saline  solution. 

(18)  Inject  this  extract  into  subcutaneous  lymph  spaces  of  a  frog. 

(19)  Observe  the  effect  of  this  injection  upon  the  second  or 
rested  frog. 

(20)  Observe  the  effect  upon  the  working  power  of  its  muscles. 


XIV.  TO  SEND  AN  ELECTRIC  CURRENT  INTO  A  NERVE  WITH- 
OUT RESPONSE.     FLEISCHL'S  RHEONOM. 

When  one  is  observing  the  effects  of  mechanical  and  thermal 
stimuli,  he  finds  that  he  may  apply  a  mechanical  stimulus  so  slowly 
that  the  nerve  may  be  severed  without  calling  forth  a  response;  he 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     57 

may  apply  heat  to  the  fresh  nerve  so  gradually  that  the  nerve  may 
l)e  actually  cooked  without  causing  a  contraction  of  the  muscle 
which  it  supplies. 

The  proljlem  which  we  have  next  to  solve  is  to  apply  an  electric 
stimulus  gradually. 

1.  Appliances.  Fleischl's  rheonom;  one  Daniell  cell;  myograph; 
contact  key;  galvanoscope;  saturated  solution  of  zinc  sulphate;  five 
wires;  frog;  operating  case. 

The  rheonom  is  constructed  as  in  Fig.  34.  Its  essential  features 
are:  g,  the  non-conducting  base  with  circular  groove;  P,  the  non- 
conducting rotatable,  central  standard;  the  battery  binding  posts, 
having  zinc  connection  with  the  groove;  the  rotating  binding  posts, 
having  zinc  limbs  dipping  into  the  groove. 

2.  Experiments  and  Observations.  Set  up  an  apparatus  as 
shown  in  Fig.  34,  after  amalgamating  the  zinc  tips  which  dip  into 
zinc  sulphate.     Fill  the  groove  with  zinc  sulphate. 

Fig.  34 


(1)  Find  and  mark  the  zero  position  for  the  rotating  limbs  of 
the  rheonom — i.  e.,  find  the  position  which  will  give  no  deviation 
of  the  detector  needle  when  the  contact  key  is  closed. 

(2)  Find  and  mark  the  position  which  the  rotating  limbs  occupy 
when  the  detector  needle  indicates  10°. 

(3)  Find  and  mark  in  succession  each  higher  increment  of  10°, 
until  the  maximum  is  reached. 

(4)  Rotate  the  limbs  so  gradually  as  to  cause  the  detector  needle 
to  rotate  with  slow  and  regular  motion  from  the  zero  position  to 
the  maximum  position  and  back. 

(5)  Make  a  gastrocnemius  muscle-nerve  preparation,  mount  it 
in  the  myograph;  change  the  wires  from  the  galvanoscope  to  the 
electrodes  of  the  myograph;  place  the  limbs  of  the  rheonom  in  the 
maximum  position;  close  the  key.  With  the  closing  of  the  key 
the  maximum  current  is  instantly  thrown  into  the  nerve  and  serves 
as  a  strong  stimulus,  in  response  to  which  the  muscle  contracts. 

((])  Place  the  limbs  of  the  rheonom  in  the  minimum  position; 
dose  the  key.  Inasmuch  as  the  muscle-nerve  preparation  is  much 
more  sensitive  to  electricity  than  is  the  low-resistance  galvanoscopy, 
the  muscle  will  probably  respond  when  the  conditions  are  as  above 
iriflifiited.     Theoretically,  a  zero  i)oint  exists.     Practically  it  may 


58  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

be  difficult  to  find  it  for  a  muscle-nerve  preparation.  The  finding 
of  a  position  where  there  is  no  response  on  closing  the  key  is,  how- 
ever, not  essential  in  this  experiment. 

(7)  Keeping  the  key  closed,  slowly  rotate  the  limbs  of  the  rheonom 
from  the  minimum  position  to  the  maximum  position.  If  the 
conditions  are  favorable  this  can  be  done  without  calling  forth  a 
response. 

(8)  Without  opening  the  key,  slowly  rotate  the  limbs  back- 
ward from  the  maximum  to  the  minimum  position.  One  may 
thus  send  through  a  nerve  a  strong  current  and  may  withdraw  the 
same  without  causing  a  contraction  of  the  muscle.  Keep  the  key 
closed. 

(9)  Quickly  rotate  the  limbs  from  minimum  to  maximum;  the 
muscle  responds.  Quickly  rotate  from  maximum  to  minimum;  the 
muscle  responds. 

From  the  preceding  observations  one  may  conclude  that  response 
to  electric  stimulation  is  elicited  not  by  the  simple  flow  of  an  elec- 
tric current  through  the  irritable  tissues,  but  by  a  more  or  less 
sudden  change  in  the  strength  of  the  current.  The  opening  and 
closing  of  a  galvanic  current,  also  its  sudden  increase  or  decrease, 
serves  as  an  efficient  stimulus,  while  the  gradual  increase  or  decrease 
in  the  strength  of  the  current  causes  no  response. 


XV.  TO   DETERMINE   THE   INFLUENCE   OF   CATHODE  AND 
ANODE  POLES. 

Many  of  the  phenomena  of  muscle-nerve  physiology  were  inex- 
plicable until  a  difference  was  noted  (von  Bezold,  1860)  in  the 
influence  of  the  anode  and  cathode.  This  difference  in  the  influ- 
ence of  the  two  poles  may  be  best  observed  by  use  of  the  sartorius 
muscle  of  a  frog. 

1 .  Appliances.  A  double  myograph  and  support ;  recording  drum ; 
Daniell  cell;  Pohl  commutator;  Du  Bois-Reymond  key;  non-polar- 
izable  electrodes;  five  wires;  electrode  clamp  and  support. 

2.  Preparation,  (a)  Set  Up  a  Pair  of  Non-polarizable  Electrodes' 
(See  Appendix,  9.) 

(b)  A  Double  Myograph.  A  most  efficient  as  well  as  convenient 
and  economical  double  myograph  may  be  arranged  for  this  experi- 
ment as  indicated  in  Fig.  35. 

Two  common  muscle  levers,  as  shown  in  the  figure,  are  used. 
These  are  held  in  position  by  common  clamps  and  heavy  support. 
The  upper  myograph  must  be  reversed  and  its  lever  counterpoised 
by  elastic  bands.  Between  the  two  myographs  a  small  wooden 
block,  with  a  longitudinal  hole  for  the  loop  of  thread  which  holds 
the  muscle,  is  held  by  a  clamp. 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     59 

3.  Experiment.     (1)  Ciirarize  a  frog.     (See  Appendix,  7.) 

(2)  After  the  lapse  of  three  hours  or  more  the  sartorius  muscle 
may  be  prepared. 

(3)  Mount  the  preparation  by  passing  a  loop  of  coarse  thread 
through  the  hole  in  the  block  W,  lift  the  muscle  by  its  tendon  of 
insertion,  pass  it  through  the  loop,  draw  the  loop  gently  around 
the  middle  of  the  muscle,  and  fix  by  making  a  single  knot  around 
the  screw  of  the  clamp.     The  fine  hooks  which  join   the   muscles 

Fig.  35 


Doable  myograph:  CI,  femur-clamp  holding  a  wooden  wedge  (W),  through  which  a  loop  of 
thread  passes.  The  sartorius  muscle  S  is  held  tightly  by  the  loop  of  thread  which  encircles  its 
middle.  The  two  tendinous  extremities  of  the  sartorius  are  hoolced  to  the  two  levers  1 1.  The 
two  levers  are  pivoted  at  P  and  P'.  The  muscle  is  put  on  a  stretch  by  the  two  rubber  bands 
r  and  r'.    The  tracing  points  Tand  7"  are  adjusted  to  a  vertical  line  on  the  kymograph  k. 


to  the  levers  may  now  be  passed  through  the  tendons,  and  the  proper 
position  of  the  levers  effected  In'  an  adjustment  of  the  clamps.  The 
loop  around  the  sartorius  may  now  be  drawn  as  tightly  as  possible 
and  not  actually  .sever  the  two  porti<Mis.  The  non-p()lariza})le  elec- 
trodes may  be  clamped  between  two  j>ieces  of  cork  and  held  by 
an  extra  support.  A  "universal"  clamp  holder  is  a  most  desirable 
acce.s.sory  to  this  apparatus. 


60  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

The  electric  apparatus  should  be  set  up  as  shown  in  Fig.  36. 

With  this  arrangement  either  electrode  may  be  made  the  anode, 
the  experimenter  needing  only  to  reverse  the  commutator  bridge  to 
reverse  the  position  of  the  anode  and  cathode. 

The  recording  drum  or  kymograph  should  rotate  rapidly.  The 
recording  points  of  the  myograph  levers  should  be  adjusted  so  that 
the  point  of  the  upper  one  touches  the  drum  vertically  over  the 
point  of  the  lower  one.  Adjust  the  marker  Cr  so  that  it  will  indicate 
the  time  making  and  breaking  the  circuit — i.  e.,  so  that  it  will  record 
on  the  drum  the  time  of  making  stimulus  and  the  time  of  breaking 
stimulus.  The  recording  point  of  the  time  marker  should,  of  course, 
be  in  the  same  vertical  line  with  the  myograph  points.  The  moist 
tips  of  the  N.  P.  electrodes  should  be  so  adjusted  as  to  touch  the 
muscle  above  and  below  the  loop  of  thread. 

Fig.  36 


(1)  Close  the  key.  If  the  preparation  has  been  successful  the 
half  of  the  muscle  in  contact  with  the  cathode  pole  will  respond 
before  the  other  one. 

(2)  Break  the  current.    The  anode  will  respond  first. 

(3)  Reverse  the  direction  of  the  current  and  repeat  (1)  and  (2). 

(4)  Vary  the  strength  of  the  current  through  use  of  the  simple 
rheocord  and  determine  whether  the  results  are  the  same  for  currents 
of  different  strength. 

Law  I.  The  make  contraction  starts  at  the  cathode  and  the  break 
contraction  starts  at  the  anode. 

When  irritable  tissue,  muscle  or  nerve,  is  subjected  to  a  galvanic 
current  the  response  to  the  stimulation  begins  in  the  region  of  the 
cathode  on  making  the  current,  and  in  the  region  of  the  anode  on 
breaking  the  current. 

Would  the  foregoing  observations  justify  the  following  statements  ? 

(1)  Cathodic  contractions,  or  make  contractions,  may  be  caused 
by  a  galvanic  current  which  is  too  weak  to  cause  anodic  contractions, 
or  break  contractions. 

(2)  Cathodic  contractions,  or  make  contractions,  are  stronger  than 
anodic  contractions,  or  break  contractions. 

Law  II.  With  a  given  strength  of  current  the  influence  of  the  cathode 
pole  is  more  irritating  than  the  influence  of  the  anode. 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     61 


XVI.  ELECTROTONUS   fTO  DETERMINE  THE  EFFECT  OF  A 

CONSTANT    CURRENT    UPON    THE    IRRITABILITY 

OF  A  NERVE). 

At  the  beginning  of  the  last  century  Ritter  discovered  that  the 
vital  properties  of  irritable  and  contractile  tissues  were  modified 
when  subject  to  a  constant  battery  current.  The  modified  con- 
dition was  called  galvanismus.  During  the  first  half  of  the  last 
century  the  subject  was  investigated  by  Nobili,  ^Nlattencci,  Valentin, 
and  Du  Bois-Reymond ;  the  last  named  substituted  the  word  electro- 
totius  for  galvanismus  and  further  modified  the  terminologv.  It 
remained  for  Pfliiger^  to  rework  the  whole  field,  to  correct,  to  elabo- 
rate, and  finally  to  formulate  laws. 

(a)  Preliminary  Experiment. 

1.  Appliances.  Muscle  signal,  or  myograph;  two  Du  Bois- 
Reymond  keys;  two  Daniell  cells;  commutator;  eight  wires;  salt. 

2.  Preparation.     Set  up  electric  apparatus  as  shown  in  Fig.  37. 

3.  Operation.  ^lake  and  mount  in  the  muscle  signal  a  gastroc- 
nemius preparation. 

Fig.  37 


4.  Observations.  (1)  In  which  position  must  the  bridge  of  the 
commutator  stand  to  give  a  descending  current  so  that  the  cathode 
will  be  nearer  to  the  muscle  than  is  the  anode?  Mark  the  opposite 
side  A. 

(2)  Fig.  37,  P,  represents  the  glass  plate  of  the  muscle  signal. 
So  arrange  the  triangular  platinum  electrodes  that  there  shall  be  a 
distance  of  alxjut  3  cm.  between  the  electrodes  and  both  electrodes 
near  that  end  of  the  plate  farthest  from  the  muscle.  Lay  the 
nerve  over  the  electrodes  and  along  the  glass  plate.  The  segment 
of  nerve  which  lies  upon  the  glass  plate  between  the  electrodes  and 
the  muscle  must  be  subject  to  various  stimuli,  mechanical  and 
chemical.  At  a  point  about  1  cm.  from  the  electrodes,  marked  X  in 
the  figure,  place  upon  the  nerve  trunk  as  many  fine  crystals  of 
common  salt  as  would  l)e  taken  up  on  the  point  of  a  penknife. 
Moisten  these  salt  crystals  with  a  drop  of  water.     While  the  salt 

'  Untersuchungcii  Uber  die  Physiologic  des  Electrotonus,  Berlin,  1859. 


62  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

solution  is  permeating  the  sheath  of  the  nerve  trunk,  adjust  the 
commutator  for  a  descending  current.  When  the  muscle  begins 
to  twitch,  note  the  effect  upon  the  signal.  The  contractions  become 
more  and  more  tetanic  in  character. 

(3)  Close  the  commutator  circuit,  open  the  short-circuiting  key — 
i.  e.,  make  the  "polarizing"  current.  If  the  experiment  is  successful 
the  tetanus  is  more  marked.    Which  pole  is  near  the  point  stimulated  ? 

(4)  Close  the  short-circuiting  key — i.e.,  break  the  "polarizing" 
current.  Reverse  the  commutator;  make  the  current.  The  muscle 
is  put  completely  or  almost  completely  at  rest.  Which  pole  is  nearer 
the  stimulus? 

(5)  Repeat  (3)  and  (4)  several  times.  It  is  evident  that  the  irri- 
tability of  the  nerve  to  the  salt  stimulus  is  increased  in  the  region 
of  the  cathode  pole  and  decreased  in  the  region  of  the  anode  pole. 
This  changed  condition  of  the  nerve  due  to  the  passage  of  a  constant 
current  is  called  electrotonus.  The  state  of  increased  irritability  in 
the  region  of  the  cathode  is  called  catelectrotonus.  The  decreased 
irritability  in  the  region  of  the  anode  is  called  anelectrotonus. 

(h)  Myographic  Record  of  Anelectrotonus  and  of  Catelectrotonus. 

1.  Appliances.  Three  or  four  Daniell  cells;  three  Du  Bois- 
Reymond  keys;  contact  key;  two  commutators;  inductorium;  two 
N.  P.  electrodes;  eighteen  wires;  kymograph;  myograph  with  moist 
chamber;  two  pairs  of  platinum-wire  electrodes  to  use  with  induc- 
tion current. 

2.  Preparation.  Arrange  apparatus  according  to  plan  as  shown 
in  Fig.  38. 

Fig.  38 


3.  Operation.  Make  and  mount  a  gastrocnemius  preparation 
in  moist-chamber  myograph,  or  frog-board  myograph.  Adjust 
electrodes  as  shown  in  diagram. 

Test  apparatus  and  preparation  by  sending  single  make  (or  break) 
induction  shocks  through  nerve  at  M.  Let  there  be  a  typical  response 
to  these  stimuli.^  The  secondary  coil  should  he  removed  to  a  distance 
that  gives  the  stimulus  of  liminal  intensity. 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     63 

To  close  the  constant  current  ''polarizes"  the  nerve,  or,  better, 
induces  electroionus. 

That  segment  of  the  nerve  between  the  anode  and  cathode  is 
called  infrapolar  region. 

Those  segments  centrally  and  distally  located  are  called  extra- 
polar. 

The  induced  current  is  called  stimulating  current. 

4.  Observations.  (1)  Adjust  for  descending,  polarizing  current. 
Stimulate  in  the  region  of  anode.  Note  extent  of  muscle  contraction. 
Induce  electrotonus;  stimulate  again  in  region  of  anode.  If  the 
experiment  is  successful  the  contraction  will  be  found  to  be  decreased 
or  absent. 

The  nerve  is  at  this  point  in  a  condition  of  anelectrotonus. 

(2)  Stimulate  at  M,  or  in  the  region  of  the  cathode.  Withdraw  the 
polarizing  current.  After  a  few  minutes  stimulate  again  at  M.  If 
the  experiment  is  successful  the  wave  is  higher  in  the  former  than 
in  the  latter  case. 

The  stimulation  was  made  in  the  region  of  the  cathode  and  the 
nerve  in  a  condition  of  catelectrotonus. 

(3)  Adjust  for  ascending,  polarizing  current. 

Stimulate  at  M — i.  e.,  in  the  region  of  the  anode.  The  contrac- 
tion is  weaker  than  in  the  normal  nerve,  or  it  may  be  cjuite  absent. 
This  region  is  now  in  a  condition  of  anelectrotonus. 

(4)  Stimulate  in  the  region  of  the  cathode.  The  response  is 
probably  weak.  Withdraw  the  polarizing  current.  Stimulate  again 
in  the  region  of  the  cathode.  The  response  is  normal — i.  e.,  it  is 
greater  than  during  the  electrotonic  condition. 

But  in  descending  extrapolar  catelectrotonus  the  response  was 
greater  than  normal.  In  the  experiment  just  performed  we  stimulate 
in  the  region  of  ascending  extrapolar  catelectrotonus.  Note  that  the 
polarizing  current  is  relatively  strong. 

Co)  Remove  one  cell  from  the  battery  and  repeat  (4).  If  the 
response  to  stimulation  is  still  weaker  with  than  without  the  polar- 
izing current,  reduce  the  strength  of  the  polarizing  current  still 
farther  by  the  use  of  the  simple  rheocord.  Finally,  with  a  weak 
polarizing  current  the  stimulus  in  the  region  of  extrapolar  catelectro- 
tonus causes  a  stronger  response  than  normal. 

The  response  which  the  muscle  makes  must  be  accepted  as  a 
measure  of  the  excitation  which  it  receives  from  the  nerve.  But 
the  excitation  flelivered  by  the  nerve  depends  upon  two  factors — 
its  irritability  and  its  conductivity.  When  the  nerve  is  stimulated 
in  the  region  of  ascending  extrapolar  or  intrapolar  catelectrotonus,  its 
increased  irritability  is  of  no  avail  if  there  is  interposed  between 
that  region  and  the  muscle  a  region  of  decreased  conductivity. 
With  strong  polarizing  current  the  region  of  the  anode  is  not  only 
df-creasefJ  in  irritability,  but  in  conductivity. 


64  EXPERIMENTAL  GENERAL  PHYSIOLOGY 


(c)  Laws  of  Electrotonus. 

(a)  The  'passage  of  a  current  through  a  nerve  induces  a  condition 
of  electrotonus  marked  by  increased  irritability  in  the  region  of  the 
cathode  (catelectrotonus)  and  decreased  irritability  in  the  region  of 
the  anode  (anelectrotonus) . 

(6)  During  electrotonus  induced  by  a  strong  current  the  conductivity 
is  decreased  in  the  region  of  the  anode.  Further — though  not  derived 
from  the  foregoing  experiment — "at  the  instant  that  the  polarizing 
current  is  withdrawn  the  conducting  power  is  suddenly  restored  in 
the  region  of  the  anode  and  greatly  lessened  in  the  region  of  the  cathode." 
— Lombard,  in  American  Text-book  of  Physiology. 


XVII.  THE  LAW  OF  CONTRACTION. 

1.  Appliances.  The  simple  rheocord;  four  Daniell  cells;  frog- 
board  myograph,  or  myograph  with  moist  chamber,  simple  key; 
Du  Bois-Reymond  key;  commutator;  two  N.  P.  electrodes. 

2.  Preparation.  Set  up  apparatus  with  four  cells  in  series,  simple 
key  as  closing  key.  Commutator  with  cross-bars;  short-circuiting 
key;  the  two  N.  P.  electrodes  clamped  in  chamber  of  myograph  or 
mounted  above  the  frog-board  myograph  (Fig.  39). 

Fig.  39 


3.  Operation.     Make  and  mount  a  gastrocnemius  preparation. 

4.  Observations.  (1)  Stimulate  with  make  and  break  of  the 
very  weakest  descending  current.  The  first  response  is  elicited  by 
the  very  weak  descending  current.  A  slightly  stronger  current  is 
required  to  elicit  a  response  with  the  ascending  current. 

Record  results  in  such  a  table  as  suggested  under  (5).  This  table 
shows  what  response  (contraction  or  rest)  the  muscle  gives  on  making 


GEXERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     65 

and  breaking  of  the  descending  current  and  on  making  and  breaking 
of  the  ascending  current. 

It  also  shows  in  a  marginal  column  the  gradual  increase  of  the 
strength  of  the  current  through  gratlual  increase  of  resistance  in 
the  rheocord. 

(2)  ]Make  and  break  with  weak  ascending  current.  If  the  con- 
ditions are  typical  the  muscle  will  contract  on  making  both  ascend- 
ing and  descending  current. 

(3j  Increase  gradually  the  strength  of  the  electrode  circuit  record- 
ing results.  After  a  longer  or  shorter  transitional  period  in  which 
the  result  will  be  characterized  by  a  contraction  on  the  make  of 
both  the  ascending  and  descending  current,  one  comes  to  a  strength 
of  current  which  causes  a  contraction  on  both  make  and  break  of 
both  descending  and  ascending  current.  This  is  the  medium  strength 
for  the  preparation  and  the  condition  in  question. 

(4)  Let  the  current  be  increased  still  farther  and  by  larger  incre- 
ments. After  passing  another  transitional  stage  one  finally  reaches 
a  strength  of  current  which  causes  a  contraction  on  make  of  descend- 
ing current  and  on  break  of  ascending  current.  This  is  the  "very 
strong"  current  for  the  preparation  under  observation. 

It  not  infrequently  happens  that  through  overstimulation  and 
fatigue  of  muscle  the  whole  experiment  cannot  be  completed  upon 
one  preparation  except  by  increasing  the  current  by  larger  incre- 
ments. 

(5)  Pfiiiger's  law  of  contraction  may  be  expressed  in  the  follow- 
in  cr  table: 


Descending. 

Ascending. 

Strength  of  current. 

Make. 

Break. 

Make. 

Break. 

Very  weak 

c 

R 

R 

R 

Weak 

cc 

R 

C 

R 

Medium 

C 

C 

c 

0 

Strong 

CC 

c 

C 

CC 

Very  strong.       .             ... 

CC 

R  (or  c) 

R 

CO 

(0)  But  how  shall  we  account  for  these  results? 

Let  us  recall  .some  of  the  laws  which  have  been  demon.strated. 

Law  I.  The  make  contraction  starts  at  the  cathode  and  the 
break  contraction  starts  at  the  anode. 

Lav:  II.  I'he  make  or  catliodic  stimulus  of  a  constant  current 
is  more  irritating  than  the  break  or  anodic  stimulus. 

Law  III.  'J'lie  pa.s.sage  of  a  con.stant  current  through  a  nerve 
iiifhires  a  condition  of  electrotonus,  marked   by  an   increased   irri- 


66  EXPERIMENTAL  GENERAL  PHYSIOLOGY 

tability  in  the  region  of  the  cathode,  and  a  decreased  irritabihty  in 
the  region  of  the  anode. 

Law  IV.  During  electro  tonus  induced  by  a  strong  current  the 
conductivity  is  decreased  in  the  region  of  the  anode  during  the 
passage  of  the  current  and  in  the  region  of  the  cathode  after  removal 
or  breaking  of  the  current. 

These  laws  account  for  all  typical  phenomena  observed  above. 


XVIII.   (a)  THE  CAPILLARY  ELECTROMETER,     (b)  THE  METHOD 
OF  USING  IT. 

In  those  experiments  where  we  have  had  occasion  to  measure 
the  strength  of  an  electric  current  or  the  difference  of  potential 
between  two  electrodes  we  have  used  the  tangent  galvanometer. 
But  in  all  these  experiments  the  strength  of  current  or  difference  of 
potential  has  been  considerable,  amounting  in  some  cases  *to  that 
represented  by  several  Daniell  cells  joined  in  series  with  a  moderate 
amount  of  external  resistance. 

To  detect  and  measure  muscle  currents  it  has  been  necessary  to 
devise  a  very  delicate  and  sensitive  instrument.  The  Wiedemann 
galvanometer  has  been  used  for  this  purpose;  but  the  most  simple 
and  satisfactory  apparatus  is  the  capillary  electrometer. 

(a)  The  Capillary  Electrometer. 

Take  a  piece  of  6-mm.  glass  tubing  and  draw  two  fine  capillary 
tubes;  clamp  these  in  burette  holders  with  the  capillaries  pointing 
vertically  downward.  Into  one  pour  a  few  drops  of  water;  it  will 
pass  through  the  capillary  and  leave  its  point  drop  by  drop.  Into 
the  second  tube  pour  some  mercury — enough  to  fill  the  capillary — 
and  stand  2  cm.  or  3  cm.  above  the  capillary  in  the  tube.  The  mercury 
will  not  flow  through  the  capillary.  Note  that  the  upper  meniscus 
of  the  water — in  the  undrawn  part  of  the  tube — is  concave,  while 
the  upper  meniscus  of  the  mercury  is  convex.  The  water  wets  the 
glass  and  seems  to  be  drawn  up  for  a  short  distance  on  the  vertical 
surface  of  the  glass,  while  the  mercury  does  not  wet  the  glass — there 
seems  rather  to  be  a  repulsion.  If  one  looks  at  the  lower  meniscus 
of  the  mercury  with  a  low-power  microscope,  he  will  find  it  to  be 
convex  downward. 

Mercury  stands  up  in  nearly  spherical  globules  on  a  glass  surface, 
and  water  forms  nearly  spherical  globules  on  an  oiled  surface.  There 
is  no  adhesion  between  the  glass  and  mercury,  while  there  is  a  strong 
cohesion  between  the  molecules  of  the  mercury.  This  accounts  for 
the  fact  that  the  mercury  forms  globules  which  but  for  the  action 
of  gravitation  would  be  quite  spherical.    If  a  drop  of  liquid  be  placed 


GESERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE    67 


upon  a  horizontal  plane  its  shape  will  be  modified  by  three  forces: 
(1)  cohesion,  (2)  adhesion,  (3)  gravitation.  In  the  case  of  the  globule 
of  water  on  an  oiled  surface,  or  of  mercury  on  a  horizontal  glass 
plane,  adhesion  is  practically  /n7,  thus  leaving  the  two  factors,  cohesion 
and  gravitation. 

Cohesion  tends  to  draw  all  the  molecules  toward  a  common  center 
and  thus  brings  the  indi\idual  molecules  of  the  surface  into  a  con- 
dition of  lateral  tension.     This  condition  is  tech- 
nically called  surface  tension.      The   greater  the  ^^^-  ^° 
preponderance  of  cohesion  over  the  other  forces 
acting   upon   the    liquid    the  greater  the  surface 
tension. 

It  is  surface  tension  which  gives  to  the  mercury 
in  the  glass  tube  a  convex  meniscus,  and  keeps  it 
from  flowing  through  a  fine  capillary  of  glass. 

It  must  be  evident  that  the  relation  between 
the  mercury  and  the  glass  (adhesion)  does  not 
vary.  If  the  position  of  the  meniscus  varies  it 
must  be  through  a  change  in  one  or  both  of  the 
other  forces  mentioned  above. 

Gravitation  measured  by  the  weight  of  the 
column  of  mercury  may  vary  by  changing  the 
height  of  the  column  of  mercury.  Through  this 
variation  the  meniscus  may  be  made  to  take  any 
flesired  position. 

Experiment  has  shown  that  the  passage  of  an 
electric  current  through  the  cohmin  of  mercury 
into  sulphuric  acid  modifies  the  surface  tension 
of  the  mercury  and  thus  changes  its  position.  As 
the  modification  of  surface  tension  varies  propor- 
tionately with  the  strength  of  the  electric  potential, 
one  may  measure  this  strength  by  noting  the 
distance    through    which    the    meniscus    moves. 

The  observation  of  the  meniscus  must  be  made  with  a  microscope, 
using  the  low  power.  Note  that  in  the  instrument  (see  Fig.  40)  the 
wooden  back  that  supports  the  instrument  is  cut  away  (at  O)  near 
the  capillary  in  order  to  permit  the  microscopic  observation  of  the 
meniscus  to  be  made  with  transmitted  light. 


Capillary  electrometer. 
(Description  in  text.) 


(h)  The  Method  of  Using  the  Capillary  Electrometer. 

'IV)  adjust  the  instrument  for  use  clean  the  capillary  absolutely 
clean  through  tlie  use  of  20  per  cent.  H^SC)^  c.  p.  and  (h'stilled  water. 
Pour  into  the  tui^e  enough  mercury  to  bring  the  meni.scus  to  the 
middle  of  the  finest  portion  of  the  capillary.  Adju.st  the  parts  of 
the  electrometer — the  pressure  bulb  /-*,  the  manometer  m,  and  the 


68 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


reservoir  R.  The  reservoir  is  partly  filled  with  mercury,  above 
which  20  per  cent.  H2SO4  c.  p.  fills  the  reservoir  to  above  the  capillary 
meniscus.  Note  that  platinum  wires  {w  w')  are  fused  into  the 
capillary  and  reservoir  passing  into  the  mercury.  These  wires  pass 
to  binding  posts  and  are  kept  in  contact  through  a  short-circuiting 
key  {K). 

The  acid  must  be  in  contact  with  the  mercury  in  the  capillary. 
To  effect  this  press  the  bulb  P  until  the  mercury  is  forced  to  the 
tip  of  the  capillary;  relieve  the  pressure  and  the  meniscus  will  recede 
drawing  the  acid  after  it.     Fig.  41  shows  how  the  electrometer  is 


Fig.  41 


Showing  method  of  joining  up  the  capillary  electrometer  E.  Note  that  the  positive  plate 
(zinc)  is  joined  through  the  rheocord  R  to  the  capillary  C,  while  the  negative  plate  (copper) 
is  joined  through  the  rheocord  to  the  reservoir.  The  battery  wires  are  joined  to  the  zero  and  1 
meter  posts  of  the  rheocord,  or  to  the  zero  and  10  meter  posts.  In  the  former  case  the  sUder 
Smust  be  very  near,  almost  touching,  the  zero  post  when  the  first  observation  of  the  change 
of  meniscus  is  made. 


to  be  joined  up  for  use.  Certain  precautions  should  always  be 
observed  in  the  use  of  the  electrometer.  The  two  poles  of  the  instru- 
ment— the  mercury  in  the  capillary  C  and  the  mercury  in  the 
reservoir — should  be  joined  through  a  short-circuiting  key,  except 
when  one  wishes  to  test  difference  of  electric  potential,  when  the 
key  may  be  opened  for  a  few  moments.  The  instrument  is  so  sensi- 
tive that  only  the  weakest  currents  should  be  allowed  to  traverse 
the  acid  between  the  poles.     The  current  from  a  Daniell  cell  is 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE    69 

much  too  strong  to  be  permitted  to  traverse  the  instrument.  In 
testing  the  instrument  with  a  Daniell  or  any  similar  cell  use  a  rheo- 
cord  joined  as  shown  in  Fig.  41,  and  make  the  first  test  with  the 
slider  almost  touching  the  zero  post,  and  subsequent  tests  with 
small  increments  until  the  movements  of  the  meniscus  are  con- 
siderable in  extent,  yet  not  so  much  as  to  carry  it  out  of  the  field 
of  the  microscope. 

If  it  is  desired  to  make  quantitative  tests  of  electromotive  force 
the  electrometer  may  be  graduated.  To  accomplish  this  it  is  neces- 
sary to  have  a  micrometer  in  the  ocular  of  the  microscope,  so  that 
the  position  of  the  meniscus  may  be  accurately  determined.  It  is 
also  necessary  to  have  some  means  of  measuring  the  force  of  dis- 
placement of  the  meniscus.  This  may  be  done  by  means  of  a  mercury 
manometer,  shown  in  Fig.  40  as  a  part  of  the  electrometer.  Pressure 
exerted  on  the  bulb  is  measured  by  the  manometer.  The  amount 
of  pressure  required  to  bring  the  meniscus  back  to  its  original  posi- 
tion after  the  opening  of  the  key  K  is  proportional  to  the  electro- 
motive force  that  displaced  the  meniscus  during  the  opening  of 
the  key. 

By  testing  a  series  of  known  values  and  taking  the  manometer 
readings  one  may  easily  determine  the  relation  between  volts  and 
millimetres  of  mercury  pressure. 


XIX.  ELECTROMOTIVE  PHENOMENA  OF  ACTIVE  MUSCLE. 

(A)  The  physioloc/ical  rheoscope,  or  the  rheoscopic  frog. 

(B)  Electromotive  force  detected  by  the  electrometer. 

In  the  process  of  dissecting  out  a  muscle-nerve  preparation  (the 
classical  form)  one  is  likely  to  drop  the  cut-off  central  end  of  the 
sciatic  nerve  upon  the  gastrocnemius  muscle.  Should  this  occur  a 
contraction  of  the  muscles  is  almost  sure  to  occur.  Galvani  made 
this  observation  and  cited  it  as  a  proof  that  electricity  exists  in 
animal  tissues. 

A  classical  experiment  well  adapted  to  demonstrate  the  difference 
of  electric  potential  in  living  tissues  is  that  known  as  the  rheoscopic 
frog. 

(A)  The  Rheoscopic  Frog. 

1.  Appliances.  Frog;  two  glass  slides,  1  inch  by  3  inches;  oper- 
ating f;i>('. 

2.  Preparation.  Pith  the  frog.  Make  two  classical  muscle-nerve 
preparations.  Place  the  two  glass  slides  end  to  end  upon  the  table 
(as  shown  in  Fig.  42j,  with  a  muscle  on  each  disposed  as  shown  in 


70 


EXPERIMENTAL  GENERAL  PHYSIOLOGY 


the  figure.  Note  that  the  nerve  from  muscle  II  touches  muscle  I  in 
two  places— at  the  end  and  middle.  Set  up  the  electric  apparatus 
for  single-induction  shocks  and  rest  the  nerve  of  muscle  I  upon  the 
electrodes. 


Fig.  42 


"The  rheoseopic  frog,"  an  experiment  to  show  the  presence  of  the  difference  of  electric 
potential  in  different  parts  of  an  active  muscle.  I.  The  active  muscle,  stimulated  at  E  by 
induction  shocks.  11.  The  second  preparation,  which  can  be  thrown  into  contraction  only 
through  some  influence  exerted  at  the  points  of  contact  (Xand  1').  Note  that  the  muscles  lie 
upon  glass  plates  (ffand  ff'),  and  that  a  glass  nerve  hook  rests  upon  /in  order  to  ensure  two 
separate  points  of  contact  of  the  nerve  from  II. 


3.  Observations.     (1)  Rule  a  table  as  follows: 


strength  of  stimulus. 


Very  weak  . 
Weak    . 
Medium 
Strong  . 
Very  strong. 
Tetanizing  . 


Eesponse. 


Muscle  I. 


Make. 


Rest. 


Break. 


Contract. 


Muscle  II. 


Make. 


Rest. 


Break. 


Rest. 


(2)  Stimulate  muscle  I  as  indicated  in  the  table  and  record  the 
response  in  the  proper  column. 

(3)  What  portion  of  preparation  I  is  traversed  by  the  electric 
current  ? 

(4)  Does  any  portion  of  the  stimulating  current  traverse  that  part 
of  muscle  I  between  the  points  X  and  Y. 

(5)  What  causes  the  contractions  of  muscle  II f  Preparation  II 
is  called  a  rheoseopic  preparation  or  a  physiological  rheoscope.  If 
the  contractions  are  caused  by  electricity  one  should  be  able  to 
detect  it  through  the  use  of  the  galvanometer  or  electrometer. 


GENERAL  PHYSIOLOGY  OF  MUSCLE  AND  NERVE  TISSUE     71 

(B)  Electromotive  Force  Detected  by  the  Electrometer. 

1.  Appliances.  A  large  frog;  non-polarizable  electrodes;  capillary 
electrometer. 

2.  Preparation.  Pith  the  frog;  prepare  electrodes,  using  kaolin 
wet  with  normal  saline  solution  for  the  tips.  Join  the  electrodes 
to  the  binding  posts  of  the  electrometer.  Make  a  muscle-nerve 
preparation,  lay  it  upon  a  glass  plate,  and  prepare  to  stimulate  with 
induction  shocks  as  in  the  case  of  muscle  I  above. 

3.  Observations.  (1)  Place  the  electrode  which  is  joined  to  the 
capillary  upon  the  tendon  of  the  muscle;  the  other  electrode  upon 
the  belly  of  the  muscle.  Adjust  the  meniscus  in  the  middle  of  the 
field  of  the  microscope.  Open  the  short-circuiting  key  of  the  elec- 
trometer while  watching  the  meniscus.  It  will  be  displaced.  Its 
displacement  suggests  a  difference  of  electric  potential  between  the 
tendon  and  the  belly  of  the  muscle.  Such  a  difference  of  potential 
is  usually  to  be  observed,  and  it  is  called  the  "demarcation  current." 
It  is  believed  to  be  due  to  the  injury  to  the  muscle  tissue  incident 
to  its  preparation.    It  is  also  called  the  current  of  injury. 

(2)  After  the  meniscus  has  come  to  rest  stimulate  the  muscle  with 
a  single  induction  shock.  The  meniscus  will  move  quickly,  but  in 
the  direction  opposite  to  that  of  its  first  motion.  That  is,  its  current 
of  action  is  greater  than  its  current  of  injury,  and  in  an  opposite 
direction.     Describe  phenomena  in  notes. 

(3)  Bring  the  muscle  into  action  through  other  stimuli  than 
electricitv  and  note  results. 


PART  II. 

SPECIAL   PHYSIOLOGY. 


CHAPTER   III. 

THE  CIRCULATION  OF  THE  BLOOD. 

I.   THE   CAPILLARY   CIRCULATION   AND   THE   MOVEMENTS   OF 

THE  HEART. 

A.  To  Observe  the  Capillary  Circulation. 

1.  Appliances.  Frog;  microscope,  with  low-power  and  high- 
power  objective;  cork  board  10  cm.  wide  by  20  cm.  or  30  cm.  long 
and  ^  cm.  thick;  pins;  operating  case;  normal  saline  solution;  watch- 
glasses;  two  100  c.c.  beakers. 

2.  Preparation.  Pin  the  frog  out,  dorsum  up,  upon  a  cork  board, 
and  bring  one  hind  foot  over  a  hole  1  cm.  in  diameter  cut  in  the 
corner  of  the  board  with  a  cork  borer.  By  tying  a  thread  to  the  second 
and  third  toes  the  web  between  these  holes  may  be  stretched  over 
the  hole  in  the  Ijoard.  Care  should  be  taken  not  to  stretch  the  web 
too  tightly  and  thus  impede  the  circulation. 

Fix  the  cork  board  with  the  frog  upon  the  stage  of  the  microscope 
in  such  a  manner  as  to  bring  the  stretched  web  over  the  middle  of 
the  stage.  Illuminate  the  web  and  focus  under  a  lower  power. 
Keep  the  web  moist. 

3.  Observations.  (1)  Observe  the  movement  of  corpuscles  within 
bloodvessels  of  varying  size  and  irregular  course.  Make  a  drawing 
of  the  field  of  observation  showing  the  relative  size,  the  course,  and 
anastomoses  of  the  bloodvessels. 

(2)  Observe  whether  the  motion  is  equally  rapid  in  all  vessels; 
if  not,  observe  whether  the  slower  currents  are  in  the  larger  or  the 
smaller  channels.  Determine  which  of  the  vessels  are  arterioles,  which 
capillaries,  and  which  venules. 

(3)  Have  you  seen  evidence  of  intermittent  force  acting  upon 
the  corpuscles?  If  so,  describe  its  influence.  Determine  whether 
this  intern)ittent  force  makes  itself  evident  in  all  the  ves.sels;  if  not, 
in  which  class  of  vessels  is  it  present? 


74  SPECIAL  PHYSIOLOGY 

(4)  Do  the  corpuscles  change  shape?    If  so;  under  what  circum- 
stances ? 

(5)  Enumerate  all  the  observed  structural  and  functional  features 
which  differentiate  arterioles  from  venules. 


B.  To  Observe  the  Action  of  the  Frog's  Heart. 

1.  Preparation.  After  the  capillary  circulation  has  been  observed, 
the  frog  may  be  pithed  and  stretched  upon  a  cork  board,  ventrum 
up.  Make  a  median  incision  through  the  skin  from  the  pelvis  to 
the  mandible;  make  transverse  incisions  and  pin  out  the  flaps. 
Raise  the  posterior  cartilaginous  tip  of  the  sternum;  insert  a  blade 
of  the  fine  scissors  under  it  and  divide  it  transversely,  about  \  cm. 
anterior  to  the  tip.  Raise  the  anterior  segment  of  the  sternum  at 
the  point  of  the  transverse  incision;  insert  the  blade  of  the  strong 
scissors  under  it  and  divide  it  longitudinally  in  the  median  line. 
Withdraw  from  the  board  the  pins  which  fix  the  anterior  extrem- 
ities; make  gentle  lateral  traction  upon  the  fore-feet  until  the  slit 
sternum  is  sufiiciently  separated  to  afl^ord  a  convenient  working 
distance  and  to  expose  the  whole  heart. 

2.  Observations.     (1)  Note  rate  of  systole. 

(2)  Note  sequence  of  contraction  of  auricles,  ventricles,  and  bulbus. 

(3)  Note  change  in  shape  of  different  parts. 

(4)  Note  the  change  in  color  and  the  position  of  the  different 
parts  of  the  heart  during  the  cycle  of  changes  that  come  with  each 
heart  beat. 

(5)  Carefully  excise  the  heart,  including  the  sinus  venosus  and 
the  bases  of  the  posterior  and  two  anterior  vense  cavse,  also  the 
bases  of  the  two  aortic  trunks.  Place  the  excised  heart  in  a  watch- 
glass.  Observe  whether  the  pulsation  continues.  If  so,  what  is 
your  conclusion  regarding  the  relation  of  the  heart  movements  to 
the  central  nervous  system? 

(6)  If  the  pulsation  continues,  note  whether  or  not  the  rate  of 
pulsation  has  been  notably  changed  by  the  excision. 

(7)  Bathe  the  heart  with  a  few  drops  of  normal  solution.  Note 
any  change  in  the  rate  of  the  beat. 

(8)  Hold  the  watch-glass  in  the  palm  of  the  hand  and  note  whether 
there  is  any  change  in  the  rate  of  the  beat. 

(9)  Float  the  watch-glass  on  ice-water  and  note  any  resulting 
modification  of  rate. 

(10)  If  the  heart  seems  vigorous  (otherwise  procure  a  fresh  one), 
carefully  sever  the  sinus  venosus  with  the  fine  scissors.  Does  the 
sinus  continue  to  beat?  Does  the  heart  continue  to  beat?  Inter- 
pretation. 

(11)  If  the  heart  beats,  sever  the  auricle  from  the  ventricle  through 
the  auriculo-ventricular  groove.     Note  results. 


THE  CIRCULATION  OF  THE  BLOOD 


75 


(12)  If  the  auricles  beat,  divide  them.  If  they  continue  to  beat, 
do  they  follow  the  same  rhythm? 

(13)  If  the  ventricle  becomes  quiescent,  stimulate  it  either  mechan- 
ically or  with  a  single  induction  shock.  How  does  it  respond  to 
a  single  stimulus?  Continue  to  subdivide  the  heart  until  the  parts 
refuse  to  respond  to  stimuli. 

(14)  Repeat  the  experiments  and  see  if  the  results  are  the  same 
on  subsequent  trials.     Note  results  and  give  your  interpretation. 

C.  To  Make  a  Graphic  Record  of  the  Frog's  Heart  Beat. 

1.  Appliances.  Large  frog;  kymograph;  heart  lever.  (For 
description  of  heart  lever  see  Appendix,  10.)  Frog-board  myo- 
graph or  similar  apparatus;  chronograph  with  a  chronographic 
system,  adjusted  to  record  seconds  upon  the  kymograph;  cover- 
glass;  normal  saline;  operating  case. 

Fig.  43 


Frog-heart  lever :  t,  tripod  to  support  lever ;  p,  the  pivot ;  c,  counterpoise  ;  h,  frog's  heart, 
on  which  the  cork  point  rests. 

2.  Preparation.  Pith  a  frog  without  destroying  its  spinal  cord. 
Take  great  care  not  to  cut  a  vertebral  artery  during  the  pithing 
operation.  Should  a  hemorrhage  occur  plug  the  opening  with 
absorbent  cotton.  Hemorrhage  depletes  the  circulatory  system,  and 
the  action  of  the  heart  is  weakened. 

In  the  operation  to  expose  the  beating  heart,  take  care  not  to  cut 
any  large  vessel,  for  the  reason  just  given.  Pin  out  the  frog,  ventrum 
up,  upon  the  frog-board  myograph.  Expose  the  heart  as  described 
in  the  previous  lesson.  CJpen  the  pericardium  carefully,  thus  expos- 
ing the  heart  to  direct  observation.  Place  some  resistant  object — 
a  cover-gla.ss,  for  example — under  the  ventricle.  So  adjust  the 
heart  lever  that  the  wedge-sha})('<l  cork  foot  of  the  long  arm  of  the 
lever  will  rest  uf)f>n  the  groove  which  marks  tiie  line  of  juncture 
between  the  aiirifle  and  the  ventricle.    (See  Fig.  43.)     If  the  weight 


76  SPECIAL  PHYSIOLOGY 

of  the  lever  seems  to  be  too  great  for  the  heart,  move  easily;  the 
long  arm  may  be  made  relatively  lighter  by  adjusting  the  counter- 
poise upon  the  short  arm.  If  the  tracing  point  of  the  long  arm 
has  a  sufficient  excursion  to  make  a  good  tracing,  bring  the  kymo- 
graph to  a  position  where  the  point  will  lightly  touch  the  carboned 
surface  of  the  drum.  The  lever  should  be  nearly  tangent  to  the 
surface  of  the  drum,  and  so  arranged  that  the  rotating  surface  of 
the  drum  turns  away  from  the  tracing  point  of  the  lever  rather  than 
toward  it. 

All  tracings  should  be  accompanied  by  a  time  tracing  or  chrono- 
gram. Study  the  chronographic  system  and  make  drawings  of  the 
plan,  showing  all  electric  connections.  Study  the  chronograph  or 
time  marker,  and  make  a  diagram  showing  its  construction. 

3.  Observations.  (1)  Note  whether  the  curve  is  a  simple  one  or 
composed  of  a  major  wave,  with  crests  superimposed  upon  it.  In 
either  case  closely  observe  the  phases  of  the  heart  cycle  and  determine 
the  relation  of  each  part  of  the  cycle  with  each  part  of  the  tracing.  If 
the  tracing  has  a  single  crest,  more  delicately  counterpoise  the  lever 
and  more  carefully  adjust  the  narrow  foot  of  the  lever  to  the  auriculo- 
ventricular  groove  and  repeat  the  experiment. 

(2)  Take  tracings  of  the  auricle  alone.  Compare  these  with  those 
of  the  auriculo-ventricular  groove  and  determine  the  causes  of 
variation. 

(3)  Without  altering  the  counterpoise  take  a  tracing  of  the 
ventricle  and  compare  it  with  the  two  preceding  curves  and  account 
for  all  the  differences. 

(4)  By  adjusting  the  foot  of  the  lever  between  the  ventricle  and 
the  bulbus  it  is  possible  to  get  a  ventriculo-bulbar  tracing  which 
differs  from  the  auriculo-ventricular  in  having  the  superimposed 
crest  following  the  ventricular  crest,  while  in  the  auriculo-ventricular 
tracing  the  superimposed  crest  precedes  the  ventricular. 

(5)  If  the  conditions  of  the  experiment  are  favorable  it  is  possible 
to  get  an  auriculo-ventriculo-bulbar  tracing.  To  get  this  the  lever 
foot  must  be  placed  in  the  auriculo-ventricular  groove  so  that  it 
rests  upon  the  auricles,  ventricle,  and  bulbus.  A  typical  tracing 
may  be  recognized  by  the  high  central  ventricular  crest  flanked  by 
two  superimposed  crests  made  by  the  auricles  and  bulbus. 

(6)  If  a  time  tracing  be  added  by  means  of  the  chronograph  one 
may  determine  the  time  relations  of  the  different  phases  of  the 
heart  cycle. 

D.  To  Observe  the  Movements  of  the  Mammalian  Heart. 

1.  Appliances.  Dog  or  rabbit;  operating  case,  supplemented  by 
haemostatic  forceps,  heavy  scissors  and  scalpels,  clippers,  heavy 
linen  thread;  hand  bellows  with  tube  and  respiration  cannula  (see 


THE  CIRCULATION  OF  THE  BLOOD  77 

Appendix,  11);  animal  holder;  morphine  solution  with  hypodermic 
syringe ;  chloroform  or  ether ;  tannic  acid ;  absorbent  cotton ;  porcelain- 
lined  trays  for  instruments;  cotton,  calipers,  and  rule. 

2.  Preparation.  The  dog  of  medium  or  large  size  is  to  be  pre- 
ferred for  class  demonstrations,  while  rabbits  or  small  dogs  may 
be  used  for  laboratory  work  by  students.  When  rabbits  are  used 
anaesthetize  with  ether.  When  dogs  are  used  anaesthetize  with 
chloroform  after  having  given  ^  to  1  grain  of  morphine  hypodermic- 
ally  fifteen  minutes  before  the  use  of  the  chloroform. 

Make  a  litre  of  one-half  saturated  solution  of  tannic  acid  to  be 
used  as  an  hpemostatic. 

3.  Operations.  (1)  To  Induce  Artificial  Respiration.  The  open- 
ing of  the  thorax  causes  the  lungs  to  collapse,  and  if  artificial  respi- 
ration were  not  instituted  the  animal  would  die  in  convulsions  in  a 
few  minutes.  The  successful  induction  of  artificial  respiration 
involves  the  opening  of  the  trachea,  insertion  of  respiration  cannula, 
and  the  maintenance  of  respiratory  movements  of  the  lungs  through 
the  use  of  the  bellows. 

Clip  the  hair  from  the  ventral  surface  of  the  neck;  make  a  median 
cutaneous  incision;  with  forceps  and  fingers  separate  subcutaneous 
tissue,  fascia,  and  muscles  over  the  middle  of  trachea,  and  clear  one 
to  two  inches  of  the  trachea;  cut  a  longitudinal  ventral  slit  into  the 
trachea  and  insert  tracheal  end  of  respiration  cannula,  ligating  it 
firmly  in  place. 

The  animal  will  now  breathe  through  the  cannula.  When  the 
thorax  is  opened — but  not  before — the  bellows  should  be  attached 
to  the  cannula  through  the  medium  of  a  rubber  tube  at  least  one 
foot  in  length,  and  the  bellows  should  then  be  brought  into  rhythmical 
action,  causing  the  lungs  to  fill  eighteen  to  twenty  times  per  minute 
in  the  case  of  a  dog  (twice  as  fast  for  the  rabbit). 

After  the  introduction  of  the  cannula  and  before  the  bellows  is 
attached  apply  the  anaesthetic  to  the  distal  end  of  the  cannula. 
When  the  l)ellows  is  attached  the  anaesthetic  must,  of  course,  be 
applied  to  the  intake  valves  of  the  bellows. 

(2)  To  Expose  the  Heart.  After  the  introduction  of  the  respiration 
■cannula,  make  a  median  incision  over  the  sternum  from  anterior 
tip  to  posterior  end  of  the  xiphoid  appendix.  Strip  the  skin  back 
laterally  as  far  as  the  junction  between  the  ribs  and  the  costal  carti- 
lages. Saturate  with  tannic  acid  solution  strips  of  absorbent  cotton 
large  enough  to  cover  all  cut  surfaces. 

With  strong  scalpel  cut  through  the  thoracic  wall  at  the  junction 
of  the  first  left  rib  with  its  cartilage,  carrying  the  incision  (piickly 
back  along  the  thorax  parallel  to  the  sternum  until  all  cartilages 
are  cut.  The  cut-oft'  ends  of  intercostal  arteries  will  bleed  freely, 
but  this  can  be  .stopped  in  a  moment  by  folding  a  strij)  of  al)sorbent 
coiUiW  wet  with  tannic  acid  over  the  cut-off  ends  of  the  ril)s.      A 


78  SPECIAL  PHYSIOLOGY 

strip  of  dry  cotton  and  a  towel  may  be  placed  outside  of  the  tannic 
acid  cotton. 

Before  proceeding  farther,  note  that  the  left  lung  is  collapsed. 
Begin  artificial  respiration,  continuing  the  rhythm  observed  in  the 
animal. 

Carry  the  incision  transversely  across  the  thorax  just  posterior 
to  the  end  of  the  sternum;  catch  the  cut-off  internal  mammary 
arteries  with  haemostatic  forceps;  carry  the  incision  forward  along- 
the  right  side  to  correspond  with  the  incision  already  made  on  the 
left  side,  and  stop  the  hemorrhage  in  the  same  way. 

The  sternum  may  be  covered  with  absorbent  cotton  and  a  towel 
and  tipped  forward  out  of  the  way. 

The  heart  is  now  clearly  exposed  within  its. pericardium,  and  its 
relation  to  other  structures  of  the  thoracic  cavity  may  be  carefully 
noted  before  the  pericardium  is  removed. 

4.  Observations.  (1)  Note  position  of  heart  with  relation  to 
lungs,  spinal  column,  diaphragm,  oesophagus,  trachea,  and  large 
bronchi. 

(2)  Note  character  of  pericardium  and  its  attachments.  Remove 
the  pericardium  by  making  a  free  longitudinal  incision  with  scissors 
and  slipping  the  heart  through  the  incision.  Note  character  of 
inner  surface  of  pericardium;  of  outer  surface  of  heart;  presence 
of  liquid  in  the  pericardium. 

(3)  Note  sequence  of  contraction  of  the  chambers  of  the  heart. 

(4)  Note  change  of  shape  of  the  heart  during  several  phases  of 
a  cardiac  cycle. 

(5)  Note  change  of  position  of  the  heart  apex  during  phases  of 
a  cardiac  cycle. 

(6)  Hold  the  beating  heart  in  the  hand  and  note  the  change  in 
the  tension  of  the  heart  muscle  during  phases  of  cardiac  cycle,, 
comparing  diastole  with  systole. 

(7)  With  calipers  and  rule  measure  carefully  changes  in  the 
diameters  of  the  heart,  comparing  end  of  diastole  with  the  end  of 
systole  and  observing  the  lateral  diameter  and  the  dorsoventral 
diameter. 

(8)  Is  there  a  change  in  the  anteroposterior  diameter — base  to 
apex?    If  so,  when  does  this  change  occur? 

(9)  "Push  the  anaesthetic"  to  the  limit  and  note  that  the  animal's 
heart  continues  to  beat.  The  same  amount  of  ether  or  chloroform 
administered  under  ordinary  conditions  would  cause  the  death  of 
the  animal  through  the  stopping  of  respiration.  But  the  respiration 
being  carried  on  artificially,  the  amount  of  chloroform  which  can 
be  taken  is  much  increased.  In  the  case  of  the  dog,  it  will  be  hardly 
possible  to  kill  with  chloroform  so  long  as  respiration  is  kept  up. 
If  the  respiration  be  stopped  the  animal  will  die  very  soon  in  con- 
vulsions. 


THE  CIRCULATION  OF  THE  BLOOD 


79 


To  terminate  the  experiment  open  the  right  ventricle.  The 
thoracic  cavity  will  quickly  fill  with  blood  and  the  animal  will  die 
a  quick  and  painless  death,  free  from  any  convulsions. 


II.  THE  APEX  BEAT  AND  THE  HEART  SOUNDS. 


1.  Appliances.  A  cardiograph,  consisting  of  a  receiving  tambour 
and  a  recording  tambour  (Fig.  44). 

The  receiving  tambour  should  be  about  4  cm.  in  diameter  and 
not  less  than  1  cm.  deep.  The  tambour  membrane  should  be  of 
dentists'  rubber-dam  and  should  be  stretched  tightly  enough  to 
give  it  a  resistance  about  equal  to  that  of  the  relaxed  biceps  muscle. 
Upon  the  middle  of  the  membrane  a  small  cork  (1  cm.  long)  is 
glued. 

Fig.  44 


The  cardiograph :  R,  receiving  tambour  provided  with  a  rubber  membrane  (m)  and  a  cork 
button  (if)  to  be  placed  on  the  apex  beat.  The  receiving  tambour  is  joined  through  the  rubber 
tube  H  to  the  tracing  tambour  T,  whose  lever  (L)  records  the  movements  of  the  thoracic  wall 
upon  the  kymograph  K. 

The  recording  tambour  should  be  3  cm.  to  5  cm.  in  diameter  and 
not  more  than  3  mm.  in  depth.  The  tracing  lever  should  be  at 
least  20  cm.  long  and  provided  with  a  delicate  celluloid  or  parch- 
ment tracing  point.  The  recording  tambour  should  be  mounted  on 
a  light  chemical  stand  and  held  by  a  universal  clamp  holder. 

The  two  tambours  sliould  be  joined  through  a  piece  of  pressure 
tubing  two  feet  in  length. 

For  construction  of  tambours  see  Appendix,  12. 

Besides  the  cardiograph  one  will  need  a  chronograph,  a  kymo- 
graph, and  a  stethcscope. 


30  SPECIAL  PHYSIOLOGY 

Study  the  new  instruments  and  make  drawings  and  diagrams 
showing  their  construction. 

2.  Preparation.  Let  a  student  remove  the  clothing  from  the 
chest.  Find  the  apex  beat.  In  which  intercostal  space  is  it  located  ? 
How  far  is  it  to  the  left  of  the  middle  of  the  sternum?  Is  the  loca- 
tion of  the  apex  beat  the  same  for  all  members  of  the  class?  In 
recording  the  location  of  the  apex  beat  refer  to  the  bony  landmarks 
of  the  chest  rather  than  to  the  nipple. 

To  take  a  cardiogram  place  the  button  (cork)  of  the  receiving 
tambour  upon  that  point  of  the  thorax  most  affected  by  heart  beat. 
The  movements  of  the  apex  of  the  heart  will  be  transmitted  and 
magnified  by  the  cardiograph.  Trace  a  cardiogram  upon  the 
kymograph. 

3.  Observations.  (1)  Take  several  cardiograms  from  the  same 
individual,  being  careful  so  to  adjust  the  apparatus  as  to  gain  the 
maximum  excursion  of  the  lever.  What  features  have  all  of  these 
tracings  in  common?  What  features  seem  to  be  accidental  and 
non-essential  ?  What  are  the  causes  of  the  essential  features  ?  What 
are  the  sources  of  the  non-essential  features? 

(2)  Take  cardiograms  of  several  individuals.  Do  all  of  them 
possess  the  features  which  seemed  essential  in  the  first  series,  taken 
from  one  individual?  If  not,  how  would  you  account  for  the  differ- 
ence. 

(3)  With  a  stethoscope,  whose  construction  you  have  carefully 
described  in  your  notes,  listen  to  the  heart  sounds  while  the  cardio- 
graph is  tracing  the  record  of  the  heart  movements.  Note  that  two 
sounds  are  audible  and  that  there  is  a  notable  pause  following  the 
shorter,  sharper  sound;  let  us  call  the  sound  which  succeeds  the 
pause  the  first  sound. 

(4)  With  what  part  of  the  cardiogram  does  the  first  sound  seem 
to  correspond  ?  With  what  part  of  the  cardiogram  does  the  second 
sound  seem  to  correspond?     Give  reasons  for  this  correspondence. 

(5)  As  far  as  the  data  will  admit,  enumerate  causes  for  the  first 
sound;  for  the  second  sound;  for  the  essential  features  of  the  cardio- 
gram. Can  one  locate  on  the  cardiogram  that  crest  or  feature  which 
corresponds  to  the  auricular  systole?  The  ventricular  systole?  The 
recoil  of  the  ventricles?  The  closure  of  the  semilunar  valves?  The 
opening  of  the  semilunar  valves? 

(6)  Giving  full  attention  to  the  auscultation  of  the  cardiac  region 
of  the  chest  with  the  stethoscope,  note  carefully:  (a)  The  point 
where  the  first  sound  is  most  distinctly  heard.  Locate  this  point 
with  reference  to  the  thoracic  skeleton,  (b)  The  point  where  the 
second  sound  is  most  distinctly  heard.  Locate  same  with  reference 
to  skeleton. 

(7)  Compare  the  two  sounds  as  to  duration,  intensity,  pitch,  and 
quality. 


THE  CIRCULATION  OF  THE  BLOOD 


81 


III.  THE  FLOW  OF  LIQUID  THROUGH  TUBES  UNDER  CONSTANT 

PRESSURE. 


Fig.  45 


The  problems  presented  by  the  circulation  of  the  blood  through 
the  bloodvessels  involve  some  of  the  general  principles  of  hydraulics. 

The  supply  of  blood  to  the  various  glands 
and  other  active  tissues  of  the  body  is 
analogous  to  the  supply  of  water  to  the 
buildings  of  a  city. 

The  blood-circulatory  system  differs  from 
the  water-circulatory  system  in  possessing 
elastic  tubes  instead  of  inelastic  ones,  and 
an  intermittent  initial  force  instead  of  the 
constant  force  furnished  by  the  "head"  of 
water  in  the  reservoir  or  stand-pipe. 

It  will  be  profitable  for  the  student  to 
make  a  few  simple  experiments  in  hydraulics 
in  order  to  make  himself  familiar  with  those 
physical  laws  which  he  will  apply  later. 

1.  Appliances.  Each  table  is  provided 
with  a  reservoir  (Fig.  45)  consisting  of  a 
galvanized-iron  reservoir  about  10  cm.  in 
diameter  and  70  cm.  in  height,  with  a  sup- 
ply tank  above.  At  the  bottom  of  the 
reservoir  there  is  a  faucet,  to  which  may 
be  screwed  a  6-mm.  nozzle  or  a  3-mm. 
nozzle,  thus  varying  the  radius  of  the  outlet 
stream. 

The  reservoir  is  supplied  with  a  gauge 
which  indicates  the  height  of  the  water  above 
the  middle  of  the  outlet  nozzle. 

Each  table  will  need  besides  the  reservoir 
tliree  6-mm.  T-tubes  and  five  6-mm.  glass 
tubes  50  cm.  long;  also  ten  rubber  connec- 
tors, a  screw  clamp,  and  centimetre  rule. 
Provide  a  large  flask  or  jar  for  catching 
discharge  and  a  .500-c.c.  graduated  cylinder 
for  measuring  the  discharge. 

2.  Preparation.  We  have  thus  a  means  of 
varying  the  radius  of  the  outlet  and  the 
height  of  the  water  above  the  outlet.    These 

are  the  two  factors  upon  which  the  fjuantity  of  the  discharge 
<lepends,  viz.,  area  of  a  cross-section  of  the  stream  and  velocity 
of  flow  of  the  stream.  The  velocity  of  flow  is  determined  by  the 
law  of  Torricelii:    "The  rate  at  which  a  fluid  is  discharged  through 

(> 


Reservoir  for  use  in  experi- 
ments in  hydraulics,  and  illus- 
trating principles  underlying 
circulation  of  the  blood. 


82  SPECIAL  PHYSIOLOGY 

an  orifice  (or  nozzle)  in  a  reservoir  is  equal  to  the  velocity  which 
would  be  acquired  by  a  body  falKng  freely  through  a  height  equal 
to  the  distance  between  the  orifice  and  the  surface  of  the  liquid." 

Make  out  a  table  which  will  show  for  each  of  the  first  five  seconds 
of  a  falling  body  the  distance  traversed  {d);  the  velocity  (v);  the 
total  height  at  the  end  of  each  second  respectively  {h) ;  and  derive 
from  this  table  the  value  of  velocity  in  terms  of  g  ((7  =  acceleration  of 
gravitation,  32  +  ft.  or  981  cm.  per  second)  and  of  t  (^==time  in 
seconds). 

(1)  V  =  gt. 

(2)  H  =  f. 

Eliminate  t  from  these  two  equations  and  express  the  value  of 
velocity  (V)  in  terms  of  the  acceleration  of  gravitation  {g)  and  the 
height  (h). 

(3)  V  =  y'2gH  =  1/2x981  H=44.3  -j/hT 

How  does  the  velocity  vary  in  terms  of  height?  The  velocity 
varies  as  the  square  root  of  the  height. 

(4)  V  x>  y^S: 

Given  the  height  of  the  water  in  the  reservoir  Qi)  and  the  radius 
of  the  nozzle  (r),  to  compute  the  discharge  (D). 

(5)  D  ^  area  X  velocity. 

(6)  D  =  7rr«  X  44.3  "i/h  =  44.3  7rr=  i/h  =  139.2  r«  -j/hT 

The  discharge  will  vary  as  the  product  of  the  square  of  the  radius 
multiplied  by  the  square  root  of  the  height. 

(7)  Door^-j/h. 

3.  Observations.  To  test  the  influence  of  the  radius  and  the 
pressure  upon  the  discharge  one  uses  the  law  (expressed  in  D  oo  r^  l/h). 
given  above.  Note  that  the  discharge  varies  with  two  different 
factors. 

It  is  a  fundamental  principle  governing  all  experimental  work, 
that,  where  one  is  studying  a  quantity  which  varies  with  two  or 
more  factors,  he  makes  all  but  one  of  the  factors  constant  and  allows 
the  quantity  in  question  to  be  modified  by  only  one  variable  factor 
at  a  time. 

We  will,  therefore,  make  the  radius  constant  by  using  the  small 
nozzle  while  we  observe  the  discharge  as  modified  by  varying  height. 

(1)  Take  the  discharge  in  c.c.  through  3-mm.  nozzle  at  ^  =  36  cm.; 
^=49  cm.;  ^  =  64  cm.: 

D  :  d  :  :  i/'H  :  i/hT 

(2)  Take  the  discharge  in  c.c.  through  6-mm.  nozzle  at  ^  =  36  cm.; 
^=49  cm.;  A,  =  64  cm.  In  these  observations  maintain  a  constant 
height  in  the  reservoir  by  letting  water  flow  in  from  the  supply  tank. 


THE  CIRCULATION  OF  THE  BLOOD 


83 


Use  a  time  unit  of  ten  seconds.     Repeat  each  observation  at  least 
three  times. 

(3)  From  the  above  results  compare  influence  of  a  varying  radius 
when  the  height  is  constant — i.  e.,  discharge  at  h  =  36,  through 
6-mm.  nozzle;  through  3-mm.  nozzle. 

D  :  d  :  :  R*  :  r2. 

(4)  Having  tested  the  two  variables  separately,  test  the  two  com- 
bined variables. 

D  :  d  :  :  R^  ^  /  g  .  jS  -j/t. 

(5)  To  determine  the  relation  of  discharge  to  resistance:  Attach 
to  the  larger  nozzle  one  length  of  6-mm.  tubing.  Note  the  discharge 
in,  say,  ten  seconds.  Attach  a  second  length  of  6-mm.  tubing,  taking 
care  that  the  tubing  is  approximately  horizontal.  Note  the  dis- 
charge in  the  same  length  of  time.  What  is  your  conclusion?  Why 
does  the  discharge  decrease  when  the  length  is  increased? 

Fig.  46 


'.V 


I  II         III        1/         T 

Reservoir  with  piezometers. 


71 


"^^ 


(6)  To  measure  the  pressure  at  various  points  along  the  course 
of  the  fli.scharge  tube:  (a)  Insert  a  6-mm.  T-tube  with  an  upright 
limb  not  less  than  50  cm.  in  length  between  the  two  6-mm.  discharge 
tubes.  Is  the  height  of  the  water  in  the  upright  (piezometer)  as 
great  as  in  the  reservoir?  (h)  Add  another  T-tube  to  the  end  of 
the  .second  6-mm.  discharge  tube;  how  high  does  the  water  rise  in 
the  second  piezometer?  Comparing  the  height  of  the  water  in  the 
reserv'oir  and  the  two  piezometers,  what  are  your  conclusions  as 
to  the  j)ressure  in  different  parts  of  the  discharge  tui)e? 

(7)  By  leaving  out  the  50  cm.  tubes  and  setting  the  T-tubes  end 
to  end  thus  (J.  X  J.  JL  J.  J.)  a  set  of  piezometers  similar  to  those  shown 
in  Fig.  46  can  be  set  up  and  new  observations  made. 


84  .    SPECIAL  PHYSIOLOGY 


IV.     THE  FLOW  OF  LIQUIDS  THROUGH  TUBES  UNDER  THE 
INFLUENCE  OF  INTERMITTENT  PRESSURE. 

A.  The  Influence  of  Intermittent  Pressure. 

1.  Appliances.  A  glass  tube  of  about  6-mm.  lumen  and  about 
100  cm.  long;  a  thin-walled  elastic  tube  of  about  the  same  lumen 
as  the  glass  tube  and  about  100  cm.  long;  a  double-valved,  strong 
rubber  bulb  (about  7.5  cm.  long);  very  thick-walled  rubber  tubing 
for  joining  up  the  apparatus;  a  2-litre  jar  and  a  flask  or  water  recep- 
tacle; heavy  linen  thread;  a  wide  capillary  and  a  jfine  capillary  or 
a  piece  of  glass  tubing  10  cm.  long  for  constructing  the  same;  500-c.c. 
graduated  cylinder;  piece  of  8-mm.  rubber  tubing  about  50  cm. 
long. 

2.  Preparation.  Join  the  large  elastic  tube  to  the  entrance  valve 
of  the  bulb.  Couple  the  glass  tube  closely  to  the  exit  valve  of  the 
bulb.  Make  all  joints  as  close  as  possible,  and  tie  tightly  with 
thread.  Draw  a  coarse  and  fine  capillary  tube  from  the  10-cm. 
piece  of  glass  tubing.  Fill  the  jar  with  water  and  immerse  the  tube 
from  the  entrance  valve  in  the  water. 

Clasp  the  bulb  in  the  hand  and  make  rhythmical  contractions  at 
the  rate  of  ten  to  fifteen  in  ten  seconds.  This  process  will,  of  course, 
pump  water  from  the  jar  into  the  flask  held  at  the  distal  end  of  the 
long  glass  tube.  One  person  should  pump  the  bulb  and  the  greatest 
care  should  be  taken  to  exert  the  same  force  and  use  the  same  rate 
in  the  several  observations. 

3.  Observations,     a.  Intermittent  force  and  inelastic  tubes. 

(1)  Does  the  stream  of  water  which  is  ejected  from  the  exit  tube 
flow  in  a  constant  or  in  an  intermittent  jet? 

(2)  Attach  a  wide  capillary  and  repeat.  What  is  the  character 
of  the  stream?    Measure  the  discharge  in  ten  seconds. 

(3)  Attach  a  fine  capillary  and  repeat.  Measure  the  discharge  in 
ten  seconds. 

b.  Intermittent  force  and  elastic  tubes. 

(4)  Disjoin  the  glass  tubing  from  the  bulb  and  join  the  100-cm. 
elastic  tube.  Work  the  bulb  as  directed  above  and  observe  the 
character  of  the  flow.     Measure  the  quantity  of  discharge. 

(5)  Join  on  the  coarse  capillary  and  repeat,  noting  the  change  in 
the  character  of  the  jet  and  the  amount  of  discharge. 

(6)  Replace  the  coarse  capillary  with  the  fine  capillary  and  repeat. 
Sum  up  results  and  formulate  conclusions. 

B.  The  Pulse  or  Impulse  Wave. 

By  putting  the  finger  upon  the  rubber  tube  while  the  bulb  is  in 
action  the  pulse  may  be  felt.     To  trace  this  upon  the  kymograph 


THE  CIRCULATION  OF  THE  BLOOD 


85 


lay  the  rubber  tube  across  the  frog-board  myograph  and  pass  a 
thread  from  the  proximal  end  of  the  board  around  the  pulsating 
tube  and  thence  to  the  thread-eye  of  the  tracing  lever  as  shown  in 
Fig.  47. 

A  block  or  cork  will  hold  the  tube  in  place.  Pulsations  of  the 
tube  will  be  transmitted  to  the  thread  and  in  turn  to  the  lever  and 
may  be  traced  upon  the  kymograph. 

Observations.  (1)  If  the  finger  be  held  upon  this  elastic  tube 
while  the  bulb  is  being  rhythmically  squeezed  a  series  of  impulses 
or  pulsations  will  be  felt  by  the  finger.  Place  one  finger  upon  the 
elastic  tube  near  the  bulb;  another  finger  near  the  capillary.  Let 
the  bulb  be  pumped  with  sudden  but  infrequent  contractions.  May 
one  note  the  difference  in  the  time  of  pulsation  felt  by  the  two 
fingers?    If  so,  which  is  felt  first,  and  why?     What  is  the  cause  of 

the  pulsation? 

Fig.  47 


Myograph  in  use  as  a  pulse-writer  :  K,  kymograph  ;  L,  tracing  lever ;  5,  short  arm  of  elbow 
lever ;  .If,  section  of  frog-board  myograph ;  T,  cross-section  of  rubber  tube ;  C,  block  of  cork 
against  which  the  tube  rests ;  WT,  weight-link  ;  P,  pivot. 


(2)  To  get  a  tracing  of  this  pulse,  pass  the  rubber  tube  across  the 
cork  board  as  shown  in  the  figure;  adjust  to  kymograph  and  'take 
tracing.  Vary  the  character  of  the  bulb  contractions  as  follows, 
taking  one  complete  rotation  of  the  drum  for  each  variation: 

(a)  Slow  initial  contraction  of  bulb  and  slow  relaxation. 

(h)  Slow  initial  contraction  of  })ulb  and  quick  relaxation. 

(c)  Quick  initial  contraction  of  bulb  and  slow  relaxation. 

(d)  Quick  initial  contraction  of  bulb  and  quick  relaxation. 

(e)  Same  as  {d)  with  slow  rhythm  (1  contraction  per  second). 
(/)  Same  as  (d)  with  rapifl  rhythm  (3  contractions  per  second). 
f3)  Make  a  careful  study  of  these  tracings  and  determine: 

(a)  The  characteristic  and  essential  features. 
(h)  The  accidental  and  non-essential  features. 

(c)  The  cause  of  the  essential  features. 

(d)  The  cause  of  the  non-essential  features. 


86  SPECIAL  PHYSIOLOGY 


V.   THE  LAWS   OF  BLOOD  PRESSURE  DETERMINED  FROM  AN 
ARTIFICIAL  CIRCULATORY  SYSTEM. 

Having  tested  by  experiment  some  of  the  laws  of  governing  the 
flow  of  liquid  through  tubes  under  the  influence  of  intermittent 
pressure,  we  come  to  the  point  where  we  may  attempt  to  reproduce 
experimentally  a  set  of  physical  conditions  so  nearly  like  those  which 
exist  in  the  animal  body  that  we  shall  be  able  to  draw  conclusions  from 
our  experiments  that  shall  hold  good  for  the  animal  circulatory  system. 

The  last  preceding  exercise  demonstrated  (1)  that  the  contin- 
uous and  even  flow  of  liquid  through  the  capillaries  is  made  possible 
by  the  elasticity  of  the  arterial  walls;  (2)  that  the  pulse  is  caused  by 
a  varying  pressure  within  the  elastic  artery;  (3)  that  the  varying 
pressure  is  due  to  the  alteration  of  systole  and  diastole  of  the  heart; 
and  (4)  that  the  pressure  within  the  arteries  is  largely  influenced  by 
the  size  of  the  capillary  through  which  the  fluid  must  pass — i.  e.,  by 
the  peripheral  resistance. 

Blood  pressure  is  then  the  product  of  two  factors:  Cardiac 
force  X  peripheral  resistance  ( P  =  H  X  R);  but  cardiac  force 
is  in  turn  due  to  the  product  of  two  factors:  Rate  X  strength; 
(H  =  r  X  s);  therefore:  Pressure  is  the  product  of  heart  rate  X  heart 
strength  X  'peripheral  resistance  (P=r  X  s  X  R)- 

We  have  here  to  deal  with  these  three  variables.  Applying  a 
principle  set  forth  in  a  previous  exercise  (to  the  effect  that  "when 
a  value  which  is  being  tested  by  experiment  is  affected  by  two  or 
more  variable  factors  only  one  of  these  must  be  allowed  to  vary  in 
any  one  experiment")  one  will  so  arrange  his  experiment  that  these 
three  factors  of  pressure  will  vary  one  at  a  time. 

1.  Appliances.  An  artificial  circulatory  system  may  be  con- 
structed as  foUows:  A  rubber  bulb  such  as  used  in  the  preceding 
exercise,  to  which  is  attached  a  capacious  entrance  tube.  To  the 
exit  tube  attach  the  100-cm.  soft-rubber  tube  used  before.  This  will 
serve  as  the  main  artery,  at  the  end  of  which  a  T-tube  may  be  inserted, 
one  limb  passing  to  the  arterial  manometer.  Beyond  the  T-tube  is 
another  rubber  tube  leading  to  a  Y-tube.  From  each  limb  of  the 
Y-tube  lead  off  a  smaller  elastic  tube,  one  branch  being  a  small,  thin- 
walled  tube  supplied  with  a  screw  clamp,  while  the  other  passes  to 
a  large  calcium  chloride  tube  which  has  been  filled  with  sponge  to 
represent  the  capillary  system  of  minute  tubes.     (See  Fig.  48.) 

After  traversing  the  capillary  system  the  liquid  is  collected  at  a  Y 
and  returns  to  the  heart  through  a  tube  which  is  nearly  twice  as 
large  as  the  artery.  In  this  vena  cava  is  inserted  a  T-tube,  to  which 
is  attached  the  venous  manometer. 

Between  the  Y-tubes  the  blood  may  be  opposed  by  high  resist- 
ance or,  with  the  screw  clamp  open,  by  the  low  resistance. 


THE  CIRCULATION  OF  THE  BLOOD 


87 


The  bulb  may  be  pumped  weak  or  strong,  fast  or  slow,  while  the 
peripheral  resistance  may  be  high  or  low.  We  have,  therefore,  a 
contrivance  through  which  we  are  able  to  vary  one  factor  at  a  time. 

The  arterial  manometer  should  have  limbs  not  less  than  50  cm. 
in  length,  while  those  of  the  venous  manometer  need  not  be  more 
than  one-half  that  length.  These  manometers  may  be  held  by 
clamps  to  chemical  stands  which  are  on  or  beside  the  table. 

2.  Preparation.  Set  up  an  artificial  circulatory  system  as  shown 
in  Fig.  48. 

Pig.  48  Fig.  49 


o'>X 


Artificial  circulatory  syBtem,  describerl  in  detail  in  text. 


Mercury  manometer. 


After  the  sy.stem  is  set  up  make  a  study  of  the  mercury  manom- 
eters, the  instruments  with  which  the  pressure  is  to  be  measured. 

The  specific  gravity  of  mercury  is  approximately  13.().  ^^hat  is 
the  gas  pressure  at  n  that  will  cause  a  rise  of  4  cm.  of  mercury  in 
the  distal  tube?     (See  Fig.  49.) 

What  is  the  water  pre.ssure  at  n  that  will  cause  a  rise  of  0  cm.  of 
mercury  in  the  distal  tube? 

What  is  the  water  pressure  at  n  that  will  cause  a  rise  of  m  cm.  of 
mercury  in  the  distal  tube? 

After  the  system  has  been  freed  from  air  and  is  at  rest,  do  the 
pro.ximal  and  distal  columns  of  mercury  in  the  arterial  manometer 


88 


SPECIAL  PHYSIOLOGY 


stand  at  the  same  lever?     If  not,  why?     What  allowance,  if  any, 
should  be  made  for  this? 

3.  Observations.     (1)  By  experiment  fill  out  the  following  table: 


Observation. 

Heart  a 
Strength. 

etivity. 
Rate. 

Peripheral 
resistance. 

Arterial 
manometer. 

"Venous 
manometer. 

1 

2  . 

3  . 

4  . 

5  . 

6  . 
7 

8       . 

Weak 
Weak 
Weak 
Weak 
Strong 
Strong 
Strong 
Strong 

Slow 
Slow 
Fast 
Fast 
Slow 
Slow 
Fast 
Fast 

Low 
High 
Low 
High 
Low 
High 
Low 
High 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

mm. 

(2)  Trace  the  pulse  upon  the  kymograph  as  indicated  in  the 
foregoing  lesson. 

(3)  What  are  the  principal  factors  which  control  blood  pressure? 

(4)  State  concisely  just  what  effect  these  factors  have  upon  blood 
pressure. 

(5)  What  combination   of   conditions   yield   the   highest   arterial 
pressure  ? 

(6)  What  set  of  conditions  yield   the  lowest  arterial  pressure? 
The  highest  venous  pressure?    The  lowest  venous  pressure? 


VI.  THE  RADIAL  PULSE  AND  THE  SPHYGMOGRAM. 

1.  Appliances.  A  sphygmograph;  tracing  slips;  a  fish-tail  gas 
jet  or  kerosene  lamp,  and  a  holder  in  which  to  place  the  slips  while 
they  are  being  smoked  (Fig.  50). 


Fig.  50 


Holder  for  smoking  slips  for  the  Dudgeon  sphygmograph. 

2.  Preparation.  That  the  sphygmograph  is  so  little  used  by  the 
general  practitioner  may  be  attributed  to  the  fact  that  hurry  of 
business  or  some  other  cause  has  hindered  him  from  making  himself 
thoroughly  conversant  with  the  adjustment  and  use  of  the  instrument, 
with  its  limitations  and  with  the  interpretation  of  the  tracings. 


THE  CIRCULATION  OF  THE  BLOOD  89 

To  Adjust  the  Sphygmo graph.  (1)  Let  the  observer  stand  with 
his  right  foot  on  a  chair.  This  brings  his  thigh  into  a  horizontal 
position. 

(2)  Let  the  snbject  stand  at  the  right  of  the  observer,  resting 
the  dorsal  snrface  of  the  left  forearm  upon  the  observer's  knee. 

(3)  Let  the  observer  with  pencil  or  pen  mark  the  location  of 
the  radial  artery. 

(4)  Let  the  observer  wind  the  clockwork  which  drives  the  tracing 
paper;  adjust  the  latter  in  readiness  for  tracing;  rest  the  instru- 
ment upon  the  subject's  arm  with  its  foot  on  the  radial  artery  and 
adjust  the  position,  tension,  and  pressure  in  such  a  manner  as  to 
obtain  the  maximum  amplitude  of  swing  of  the  tracing  needle. 
Take  the  tracing.     Fix  in  damar-benzole  solution. 

3.  Observations,  a.  The  Location,  etc.,  of  the  Radial  Artery.  (1) 
What  are  the  relations  of  the  radial  artery  at  the  distal  end  of  the 
radius  ? 

(2)  How  may  the  relations  vary? 

(3)  Is  there  any  variation,  among  the  members  of  the  division, 
in  the  location  of  the  radial  artery? 

(4)  ^lay  excessive  muscular  development  affect  the  ease  with 
which  the  artery  may  be  located  and  its  pulsations  studied? 

(o)  ^lay  excessive  deposit  of  adipose  tissue  hinder  the  observations 
of  the  pulse? 

(6)  May  faulty  position  of  subject  or  of  his  clothing  affect  the 
pulse  ? 

b.  The  Digital  Observation  of  the  Radial  Pulse.  (7)  Feel  the 
pulse  with  the  side  or  back  of  the  finger,  then  with  volar  surface  and 
tip  of  each  finger  of  each  hand,  and  note  the  finger  or  fingers  with 
which  the  feeling  is  most  acute.  It  will  be  wise  to  always  use  these 
fingers  in  all  tactile  examinations.  Their  acuteness  of  feeling  will 
increase  with  practice.  One  may  thus  acquire  the  educated  touch 
— tactu-f  eruditus. 

(5)  How  much  may  be  learned  of  the  pulse  by  means  of  the  touch 
alone?  Observe  and  note:  (a)  rate;  (b)  rhythm;  (c)  volume;  {d) 
strength;  ie)  compressibility;  (/)  may  anything  else  be  determined 
by  this  method  ? 

c.  The  Sphygmogram.  (9)  Take  at  least  three  pulse  tracings  of 
each  individual  in  the  division,  (a)  Compare  the  tracings  taken 
from  one  individual;  if  they  cHffer,  determine  the  cause  of  the  differ- 
ence, (b)  Compare  the  tracings  of  (h'fferent  members  of  the  division. 
Determine,  if  possible,  the  cause  of  the  differences. 

nOj  1  )o  variations  of  the  relations  of  the  artery  affect  the  s})hygmo- 
gram?  Does  the  adjustment  affect  the  sphygmogram?  Does  the 
elasticity  of  the  artery  affect  the  tracing?  How  does  strength  or 
rate  of  heart  beat  affect  it? 

Make  a  list  of  the  facts  regarding  the  condition  of  the  circulatory 


90 


SPECIAL  PHYSIOLOGY 


system  which  may  be  determined  with  the  help  of  the  sphygmograph. 
Make  a  hst  of  the  precautions  to  be  observed  in  the  use  of  the  sphyg- 
mograph. 

The  Carotid  Pulse. 

One  will  frequently  experience  difficulty  in  taking  the  radial  pulse; 
in  fact,  not  more  than  one  person  in  three  or  four  is  a  favorable 
subject  for  this  observation.  The  reason  for  this  is  not  far  to  seek. 
Anything  beyond  a  moderate  development  of  the  musculature  of 
the  forearm  is  accompanied  by  such  development  of  the  tendons 
and  of  the  styloid  process  of  the  radius  that  the  artery  is  quite  in- 
accessible for  the  sphygmograph-foot  as  usually  constructed.  A 
moderate  deposit  of  subcutaneous  fat  also  obscures  the  radial 
pulse  and  makes  the  use  of  the  sphygmograph  most  unsatisfactory. 

Fig.  51 


Porter's  carotid  sphygmograph :  R,  receiving  tambour  in  form  of  open  bell,  that  is  pressed 
against  the  throat  over  the  common  carotid  ;  T,  tracing  tambour  with  small,  thin  membrane  and 
light  lever. 

The  simple  sphygmograph  devised  by  Dr.  Porter,  of  Harvard, 
enables  one  to  overcome  some  of  the  difficulties  mentioned  above. 
This  instrument  consists  (1)  of  a  very  small  and  delicately  adjusted 
recording  tambour  with  high  magnification  and  a  delicate  tracing 
point;  (2)  of  a  receiving  tambour  not  over  2  cm.  or  3  cm.  in  diameter 
and  at  least  1  cm.  deep,  connected  with  the  recording  tambour 
through  a  50-cm.  piece  of  pressure  tubing,  which  is  provided  with  a 
side  vent  closed  by  a  clamp.  For  the  receiving  tambour  a  small 
thistle  tube  may  be  used.     (See  Fig.  51.) 


THE  CIRCULATION  OF  THE  BLOOD  91 

To  trace  the  carotid  pulse,  place  the  open  mouth  of  the  receiving 
tambour,  over  which  no  membrane  has  been  stretched,  over  the 
course  of  the  carotid  arterv  beside  the  hirvnx,  taking  care  that 
the  side  vent  of  the  pressure  tube  is  open  while  the  adjustment 
is  being  made.  Close  the  vent,  and  if  the  adjustment  has  been 
successful  the  lever  will  show  the  carotid  pulse.  Trace  it  upon  the 
kymograph. 

Compare  the  carotid  sphygmogram  with  the  radial  sphygmogram. 
Account,  if  possible,  for  any  essential  difference. 

One  may  trace  a  radial  sphygmogram  with  the  same  instrument 
by  stretching  a  rubber  membrane  rather  tightly  across  the  mouth  of 
the  receiving  tambour  cementing  a  bone  collar-button  to  the  middle 
of  the  membrane  then  placing  the  head  of  the  collar-button  upon 
the  radial  arterv. 


VII.  TO  DETERMINE  THE  ARTERIAL  BLOOD  PRESSURE  IN  AN 

ANIMAL. 

1.  Appliances.  Dog  or  a  large  rabbit;  mercurial  manometer, 
with  manometer  tambour.  (See  Appendix,  13.)  In  lieu  of  the 
manometer  tambour  (Fig.  52)  one  may  use  the  ivory  float  with 
tracing  point  in  the  distal  limb  of  the  manometer;  kymograph; 
chronograph;  physiological  operating  case;  glass  arterial  cannulte; 
half-saturated  solution  of  sodium  carbonate,  sodium  sulphate,  or 
magnesium  sulphate;  clippers;  dog  board  or  rabbit  holder;  absorb- 
ent cotton;  one-half  grain  of  sulphate  of  morphine;  hypodermic 
.syringe;  chloroform  and  ether. 

2.  Preparation.  The  manometer  should  be  filled  with  mercury 
with  at  least  10  cm.  in  each  limb.  Attach  to  the  proximal  limb 
of  the  manometer  a  piece  of  pressure  tul)ing  G  or  S  inches  in  length, 
to  which  attach  one  limb  of  a  T-tube.  To  the  opposite  limb  of  the 
T-tube  attach  another  piece  of  pressure  tubing  not  less  than  a  foot 
in  length,  into  the  end  of  which  the  glass  cannula  can  be  placed. 
To  the  side  limb  of  the  T-tube  attach  a  rubber  tube,  which  may  be 
carried  upward  to  an  inverted  flask  filled  with  the  non-coagulant 
(XajCO,,  XajSO^  or  MgSOj.  The  tube  leading  from  the  reservoir 
shoulfl  have  a  screw  clamp  near  the  T-tube.  The  reservoir  may 
be  suj)})orted  near  the  top  of  the  same  stand  which  supports  the 
manometer. 

If  a  dog  is  used  for  the  ex})erinient  he  should  be  given  from  -\  to 
^  grain  of  morphine  twenty  minutes  before  the  an.esthesia  with 
chloroform.     If  a  large  rabbit  is  used  anaesthetize  with  ether. 

'.).  Operation.  After  fastening  the  animal  to  the  holder,  clip  the 
throat,  make  an  incision  from  the  uj)per  end  of  the  sternum  over 
the  right  sternothyroid    nuiscle  to  the  middle  of    the  neck,  cutting 


92 


SPECIAL  PHYSIOLOGY 


through  the  skin  and  subcutaneous  tissue  to  the  surface  of  the  muscle. 
The  external  jugular  vein  lies  close  to  the  incision  externally. 

Sponge  the  oozing  vessels  until  hemorrhage  is  checked,  then  using 
forceps  and  fingers  dissect  away  the  fascia  until  you  reach  the  external 
margin  of  the  sternothyroid  muscle.  Separate  this  muscle  to  the 
inside,  making  an  opening  down  to  the  carotid  artery,  where  pulsation 
may  be  felt  near  the  trachea.  Lifting  the  sheath  which  contains  the 
carotid  artery  and  the  vago-sympathetic  nerve,  taking  care  not  to- 


Fig.  52 


The  manometer  tambour :  if,  manometer ;  Tb,  tambour ;  R,  reservoir  filled  with  one-half 
saturated  solution  Na.COa;  T,  T-tube ;  Pt,  pressure  tube:  CI,  clamp;  C,  cannula;  P,  proximal 
hmb  of  manometer  ;  D,  distal  limb  of  manometer ;  t,  tracing  point  of  tambour  lever. 

wound  the  internal  jugular  vein,  which  lies  in  close  relation  to  these 
structures,  tear  open  the  sheath  of  the  artery  and  nerve  and  separate 
out  the  carotid  artery  to  the  extent  of  one  or  two  inches. 

Choose  a  glass  cannula  not  larger  than  the  carotid;  place  the 
large  end  of  the  cannula  in  the  pressure  tubing  attached  to  the 
manometer.  Open  the  screw  clamp  and  allow  the  tubes  to  fill  with 
the  solution  clear  to  the  point  of  the  cannula.     Close  the  screw 


THE  CIRCULATION  OF  THE  BLOOD  93 

clamp  to  stop  the  flow  of  the  sokition  from  the  reservoir  and  do  not 
open  the  clamp  after  this  except  to  clear  the  cannula  of  a  clot;  and 
this  cannot  l)e  done,  of  course,  while  the  cannula  is  in  the  arterv. 
Ligate  carotid  artery  at  the  upper  end  of  the  incision.  Clamp  the 
lower  portion  of  the  carotid  with  the  seraphin  forceps,  place  the 
finger  under  the  artery,  make  a  longitudinal  incision  in  the  middle 
of  the  exposed  portion  of  the  carotid.  Insert  the  point  of  the  cannula 
into  the  lumen  of  the  artery,  tie  the  cannula  in  place,  and  remove  the 
seraphin  forceps. 

4.  Observations.  As  soon  as  the  seraphin  forceps  have  been 
removed  the  blood  will  rush  into  the  cannula  and  tube  for  a  dis- 
tance of  4  to  8  cm.,  the  mercury  will  rise  in  the  distal  limb  of  the 
manometer  to  a  corresponding  degree. 

(1)  Measure  this  rise  in  the  distal  limb  of  the  manometer.  What 
is  the  blood  pressure  in  centimetres  of  mercury  per  unit  area? 

(2)  Note  that  the  mercury  rises  and  falls  in  the  manometer  with 
a  rh\i:hmical  motion.  Attach  the  manometer  tambour  or  adjust  the 
float  and  watch  the  movements  of  the  tracing  point.  Feel  the  pulse 
of  the  animal  and  note  whether  the  movements  of  the  tracing  point 
correspond  to  the  heart  beats. 

(3)  Bring  the  kymograph  into  position,  adjust  the  tracing  point 
of  the  blood-pressure  apparatus,  also  the  chronograph,  and  take  a 
tracing.     What  is  the  rate  of  heart  beat? 

(4)  Are  the  respiratory  movements  evident  in  the  tracing?  If  so, 
what  is  the  influence  of  inspiration  upon  blood  pressure?  What  is 
the  influence  of  expiration?  Account  for  the  influence  of  respira- 
tory movements  upon  blood  pressure. 

(5)  What  causes  the  blood  pressure  to  rise  during  inspiration? 
Modification  in  blood  pressure  must  be  due  either  to  the  rate  or 
strength  of  the  heart  beat  or  to  the  condition  of  peripheral  resistance. 

(6)  If  a  line  were  drawn  through  the  lowest  point  of  the  individual 
cardiac  waves,  this  waving  line  would  represent  the  influence  of 
respiratory  movements  upon  blood  pressure.  If  the  lowest  point 
of  these  respiratory  waves  were  joined  by  a  line,  would  this  line 
be  a  straight  one  or  would  it  be  a  long,  undulating  curve?  If  such 
a  curve  is  observed,  it  may  be  recognized  as  the  Traube-Hering 
curve.  This  curve  represents  a  gradual  rise  and  fall  of  the  l^lood 
pressure  under  the  influence  of  changing  peripheral  resistance, 
which  in  turn  is  controlled  bv  the  vasomotor  nerve  centres. 


VIII.    THE  SPHYGMOMANOMETER  AND  PULSE  PRESSURE. 

\'arious  clinical  instruments  have  been  devised  for  the  purpose 
of  determining  blood  pressure  in  the  human  subject  in  health  and 
in  disease.     The  most  satisfactorv  of  these  devices  involves  the  use 


94 


SPECIAL  PHYSIOLOGY 


of  the  mercury  manometer  in  measuring  the  pressure  in  a  pneumatic 
arm-girdle  so  adjusted  as  to  suppress  or  to  modify  the  pulse.  An 
accurate  determination  of  blood  pressure  is  occasionally  of  very  great 
importance,  and  it  goes  without  saying  that  methods  used  on  the 
lower  animals  are  not  applicable  in  the  case  of  man  because  they 
involve  the  opening  of  an  artery. 

The  only  appliafice  needed  is  the  sphygmomanometer  (Fig.  53) 
and  the  only  preparation  is  for  a  member  of  the  class  to  remove 
clothing  from  one  arm. 

Observations.  (1)  Let  the  subject  lie  upon  his  back  on  the 
table  in  an  easy  and  comfortable  position,  and  absolutely  relaxed 
and  quiet  for  five  minutes.     During  this  period  the  girdle  may  be 


Fig.  53 


The  sphygmomanometer :   G,  arm-girdle  with  inflatable  rubber  tube  (t)  within  and  sole-leather 
belt  (6)  without ;  P,  pressure  bulbs  ;  m,  mercury  manometer. 

fastened  about  the  right  arm.  While  one  observer  is  counting  the 
pulse  at  the  left  wrist,  another  may  feel  the  right  pulse.  A  third 
observer  may  watch  the  manometer  while  he  gradually  pumps  air 
into  the  girdle  until  the  pulse  is  shut  off  at  the  wrist.  Read  the 
manometer,  relax  the  girdle  pressure  until  the  pulse  reappears. 
Read  the  manometer.  The  mean  between  the  two  readings  as  thus 
made  is  taken  to  represent  the  pulse  pressure.  Record  the  pulse 
rate  as  counted  on  the  left  pulse.  Record  the  pulse  pressure  as 
determined  by  the  sphygmomanometer. 

(2)  Let  the  subject  lie  on  his  right  side.     Take  observations  as 
outlined  above  and  record  pulse  rate  and  pulse  pressure. 


THE  CIRCULATION  OF  THE  BLOOD  95 

(3)  Let  the  subject  lie  on  his  left  side.     Record  results. 

(4)  Let  the  subject  sit.     Record  results. 

(5)  Let  the  subject  stand.    Record  results. 

(6)  Let  the  subject  take  vigorous  exercise  for  five  minutes.  Take 
observations  of  pulse  rate  and  pulse  pressure  while  the  subject  stands. 

(7)  From  the  tabulated  results  of  the  above  observations  write  in 
a  list  the  postures  and  conditions  which  give  an  increasing  series  of 
pulse  pressures. 

(S)  Prepare  a  similar  list  of  the  postures  and  conditions  which 
give  an  increasing  series  of  pulse  rates. 

(9)  Are  these  two  series  alike  in  the  order  in  which  the  conditions 
are  named? — i.  e.,  do  the  conditions  which  give  high  rate  give  also 
high  pressure?    Account  for  what  you  discover. 

(10)  If  pulse  rate  increases,  under  what  conditions  could  pulse 
pressure  fall  {P=Hr  X  Hs  X  R)"^ 


IX.     TO  DETERMINE   THE  INFLUENCE  OF  THE  VAGUS  NERVE 
UPON  THE  ACTION  OF  THE  HEART. 

1.  Appliances.  Operating  case;  a  pair  of  curved,  blunt-pointed 
shears,  or,  better,  a  pair  of  barber's  clippers;  a  rabbit  board;  a  large 
sheet  of  heavy  paper;  cotton;  ether;  thread;  one  dry  cell;  induc- 
torium;  shielded  electrode  (Fig.  54);  seven  wires;  stethoscope;  a 
rabbit;  contact  key;  short-circuiting  key. 

Fig.  54 


A  shielded  electrode  of  hard  rubber,  bearing  copper  or  platinum  wires. 

2.  Preparation.  Let  six  or  eight  students  be  divided  into  three 
or  four  groups  of  two  each. 

Let  the  group  "a,"  be  responsible  for  the  anaesthesia.  Use  the 
sheet  of  heavy  paper  to  make  a  conical  hood,  whose  spiral  turns  may 
be  held  in  place  with  sealing-wax  or  pins.  Place  a  wad  of  cotton 
loosely  in  the  mouth  of  the  cone. 

Let  the  group  "b"  perform  the  operation.  Tie  the  rabbit  back 
downward  upon  the  holder;  fix  the  nose  in  special  holder;  with  the 
barber's  cjij>pers  remove  the  hair  from  the  ventral  side  of  the  thorax 
and  neck;  make  hanfls  and  instruments  clean;  place  instruments  in 
shallow  basin  of  warm  water;  cut  two  or  three  ligatures  of  thread 
anri  place  them  in  the  in.strument  basin. 

Let  the  group  "c"  arrange  the  electric  apparatus  for  stimulation 


96  SPECIAL  PHYSIOL OGY 

of  the  nerves.  Fill  the  cell;  join  up  with  contact  key  in  the  primary 
circuit,  and  a  short-circuiting  key  in  the  secondary  circuit.  Test 
the  apparatus  to  see  if  everything  is  in  order.  Group  "d"  should 
keep  all  the  records  of  pulse  or  other  observations. 

3.  Operation.  Group  "a."  (1)  Pour  1  c.c.  or  2  c.c.  of  sulphuric 
ether  upon  the  cotton  in  the  cone;  place  the  cone  over  the  rabbit's 
nose;  observe  and  note  carefully  the  three  stages  of  anaesthesia. 

(2)  Carefully  note  the  rate  of  the  heart  before  beginning  anaes- 
thesia, and  the  influence  of  anaesthesia  upon  rate  and  strength  of 
heart  and  respiration. 

(3)  Keep  the  cotton  moist  with  ether;  watch  the  respiration  and 
pulse,  and  be  careful  not  to  give  the  animal  too  much  and  thus 
interrupt  the  experiment. 

Group  "b."  Wash  the  clipped  surface  of  the  throat.  After  the 
rabbit  is  completely  anaesthetized,  make  with  scissors  a  median 
incision  through  the  skin,  beginning  at  the  anterior  end  of  the  sternum 
and  cutting  anteriorly  for  about  5  or  6  cm. ;  divide  the  subcutaneous 
connective  tissue  over  the  middle  of  the  trachea.  Carefully  separate 
from  the  median  line  on  either  side  laterally  the  subcutaneous  con- 
nective tissue  with  the  associated  adipose  tissue. 

How  many  pairs  of  muscles  come  to  view?  What  two  muscles 
approach  the  median  line  to  form  the  apex  of  a  triangle  at  the  anterior 
end  of  the  sternum?  Observe  a  pair  of  thin  muscles  lying  dorsal 
to  the  muscles  just  mentioned,  and  joining  them  in  the  median  line 
to  form  a  thin  muscle  sheet  covering  the  trachea  on  its  ventral  side. 
What  muscles  are  these? 

Carefully  lift  up  the  median  edge  of  the  sternomastoid  muscle 
and  separate  with  the  handle  of  a  scalpel  or  a  seeker  the  delicate 
intermuscular  connective  tissue.  A  bloodvessel  and  several  nerves 
come  into  view. 

Is  the  bloodvessel  an  artery  or  a  vein?  How  many  large  nerves 
accompany  the  bloodvessel? 

Take  hold  of  the  sheath  of  the  vessel;  lift  it  up  and  note  in  the 
connective  tissue  accompanying  the  bloodvessels  two  nerves,  one 
large  and  one  small.  When  the  artery  is  in  its  normal  position, 
what  relation  do  these  two  nerves  sustain  to  it  ?  Which  of  the  two 
nerves  is  external  and  which  is  dorsal  to  the  bloodvessel?  Which 
is  in  close  relationship  with  the  artery?  The  larger  of  the  two 
nerves  is  the  vagus  or  pneumogastric. 

In  preparing  the  nerve  for  stimulation  one  should  neither  grasp 
it  with  the  forceps  nor  with  the  fingers.  It  may  be  separated  from 
the  delicate  connective  tissue  in  which  it  lies  by  use  of  a  blunt  seeker. 
Far  better  than  any  metallic  instrument  is  a  small  glass  rod  drawn 
to  a  point,  curved  and  rounded  in  the  Bunsen  lamp.  Prevent  the 
tissues  drying  up  by  occasionally  pressing  them  lightly  with  pledgets 
of  cotton  moistened  with  normal  salt  solution.    Adjust  the  electrode 


THE  CIRCULATION  OF  THE  BLOOD  97 

carefully  upon  the  vagus  and  see  that  no  unnecessary  tension  is 
allowed  to  be  exerted  upon  the  nerve.  It  is  usually  necessary  to 
hold  the  electrode  in  place  during  the  observations. 

4.  Observations,     a.  Anaesthesia.     (Observations  of  Group  "a.") 

(1)  Are  you  able  to  make  out  the  different  stages  of  anaesthesia  ? 

(2)  How  many  stages  did  your  animal  manifest? 

(3)  Give  the  characteristics  of  each  stage? 

(4)  AVhat  effect  did  the  ether  have  upon  the  rate  of  heart  beat? 

(5)  What  effect  did  ether  have  upon  respiration? 

b.  The  Stimulation  of  the  Vagus.  (Observations  of  Groups  "c" 
and  "d.") 

(6)  Stimulate  moderately  one  vagus.  Note  with  a  stethoscope  any 
change  in  the  rate  of  the  heart. 

(7)  Cut  both  vagi  high  up  in  the  neck.  Note  the  rate  of  heart 
beat  at  intervals  of  five  minutes  for  thirty  minutes,  allowing  the 
rabbit  to  partially  recover  from  the  anaesthesia. 

(8)  Stimulate  one  vagus.  Compare  the  result  with  that  obtained 
under  experiment  (6). 

(9)  Will  very  strong  stimulation  bring  the  heart  to  a  standstill? 

(10)  If  the  heart  were  brought  to  a  complete  standstill  by  the 
stimulation,  will  it  start  up  spontaneously  when  the  stimulus  is 
removed?  Will  the  rate  be  the  degree  of  acceleration  observed  in 
experiment  (7)? 

(11)  Sum  up  the  observations  into  a  concise  statement  as  to  the 
influence  of  the  vagus  upon  the  heart. 

Note.     Dispatch  the  rabbit  with  chloroform. 


X.    TO   DETERMINE   THE   INFLUENCE   OF   THE   CARDIAC 

SYMPATHETIC  NERVES  UPON   THE  ACTION 

OF   THE  HEART. 

The  appliances  should  be  the  same  as  for  the  preceding  exercise. 

Let  the  students  who  work  at  one  table  continue  the  same  grouping 
that  was  arranged  in  the  preceding  exercise,  but  rotating  in  the 
work:  Group  "a"  to  operate;  group  "b"  to  arrange  electric 
apparatus  and  stimulate  nerve;  group  "c"  to  note  pulse  rate  and 
keep  records;  group  "d"  to  give  anaesthetic. 

The  operation  should  be  similar  to  that  of  the  vagus  experi- 
ment. 

Find  the  cardiac  branch  of  the  cervical  sympathetic  in  the  lower 
part  of  the  neck,  where  it  is  in  close  relation  with  the  carotid  artery 
and  the  internal  jugular  vein.  The  most  certain  way  to  recognize 
it  is  through  its  function.  Carefully  separate  out  the  nerve  trunks 
in  the  region  described;  with  the  glass  nerve  hook  lift  up  any  nerve 
except  the  vagus  and  stimulate  nuxlerately. 

7 


98  SPECIAL  PHYSIOLOGY 

Stimulation  of  the  cardiac  sympathetic  distinctly  increases  the 
pulse  rate. 

Find  the  corresponding  nerve  of  the  opposite  side,  verifying  your 
choice  by  observing  the  effect  of  stimulation. 

Cut  both  cardiac  sympathetic  nerves  and  observe  the  rate  of  the 
heart  beat  at  intervals  of  five  minutes  through  a  period  of  thirty 
minutes. 

XI.  THE  INFLUENCE  OF  THE  VAGUS  AND  THE  CARDIAC 
SYMPATHETIC  UPON  THE  ARTERIAL  BLOOD  PRESSURE. 

1.  Appliances.  Dog  or  large  rabbit;  animal  holder;  mercury 
manometer,  with  float  or  tambour  and  with  flushing  flask  of  non- 
coagulant;  with  tubing  and  cannulse,  as  described  in  Appendix  A, 
12;  a  kymograph,  inductorium;  Daniell  cell;  two  Du  Bois-Reymond 
keys;  operating  case;  chloroform,  ether,  morphine;  hypodermic 
syringe. 

2.  Preparation.  Let  eight  students  in  four  groups  of  two  each 
have  charge  of  (a)  anaesthesia,  (6)  operations,  (c)  electric  apparatus 
and  stimulation,  {d)  pressure  tracings. 

3.  Operations,  (a)  Aneesthetize  the  animal  in  accordance  with 
directions  given  in  previous  exercises  for  the  dog  and  rabbit,  respec- 
tively. 

(h)  Remove  the  hair  from  the  throat;  make  a  cutaneous  incision 
in  the  median  ventral  line  from  the  anterior  end  of  the  sternum  to 
the  anterior  end  of  the  larynx.  Remove  the  subcutaneous  tissue 
and  expose  the  sternomastoid  and  sternothyroid  muscles.  Let  one 
operator  expose  the  carotid  artery  of  one  side  while  the  other  operator 
exposes  the  vagus  and  sympathetic  of  the  other  side. 

(c)  Adjust  the  shielded  electrode  for  stimulation.  Insert  the 
cannula  into  the  artery. 

{d)  Make  the  tracing  of  arterial  blood  pressure  in  accordance  with 
directions  given  in  a  previous  exercise. 

While  the  tracing  is  in  progress  stimulate  the  vagus  with  a  moderate 
tetanizing  current  for  a  period  of  two  to  five  seconds.  Repeat  the 
stimulation  at  intervals  of  ten  to  twenty  seconds  for  ten  minutes. 

Adjust  the  electrode  for  stimulation  of  the  cardiac  sympathetic. 
Stimulate. 

4.  Observations.  (1)  What  is  the  average  blood  pressure  meas- 
ured in  centimetres  of  mercury  in  the  animal  under  observation 
before  stimulation  of  a  nerve? 

(2)  What  influence  does  stimulation  of  a  vagus  nerve  have  upon 
the  arterial  blood  pressure? 

(3)  Is  the  effect  clearly  marked  on  the  pressure  tracing? 

(4)  What  influence  does  stimulation  of  the  cardiac  sympathetic 
have  upon  arterial  blood  pressure? 


THE  CIRCULATION  OF  THE  BLOOD 


99 


(5)  Is  the  effect  clearly  marked  on  the  pressure  tracing? 

(6)  In  the  case  of  which  nerve  is  the  influence  of  stimulation  the 
more  pronounced? 

(7)  In  one  animal  cut  both  vagi  nerves  and  note  the  influence  on 
blood  pressure  for  a  period  of  one  hour  after  the  section, 

(8)  In  another  animal  cut  both  cardiac  s^Tnpathetic  nerves  and 
note  the  influence  on  blood  pressure. 


XII.    THE    BLOOD   PRESSURE    IN    THE   TISSUES. 


Fig.  55 


A.    To  Determine  Capillary  Blood  Pressure. 

1.  Appliances.  A  set  of  metric  weights  from  1  to  100  grams; 
a  common-sized  watch-crystal;  a  |-inch  round  cover-glass,  No.  3; 
sealing-wax;  linen  thread;  dividers;  millimetre  scale. 

2.  Preparation.  To  make  an  apparatus  for  determining  capillary 
pressure  mark  upon  the  edges  of  the  watch-crystal  and  cover-glass, 
points  distant  from  each  other  120°  of 
arc,  cut  three  equal  pieces  of  thread  from 
10  to  12  cm.  in  length;  fasten  the  ends  to 
the  points  marked  in  the  circumference 
of  the  glasses  with  melted  sealing-wax.  If 
the  threads  are  of  equal  length,  and  if  the 
cover-glass  is  held  in  a  horizontal  plane, 
the  watch-crystal  suspended  by  the  threads 
should  be  parallel  to  the  cover-glass,  and, 
therefore,  in  an  horizontal  plane.  If  the 
cover-glass  is  given  a  half-turn  to  right  or 
left,  the  three  threads  will  cross  as  seen  in 
Fig.  5.5.  A  thread  should  be  tied  around 
where  this  cross  occurs  and  the  knot  se- 
cured with  sealing-wax.  Weigh  this  ap- 
paratus and  mark  upon  the  watch-glass 
its  weight  in  grams. 

Hold  the  left  hand  with  palm  upward, 
fingers  slightly  flexed.  Hold  the  apparatus 
with  the  cover-glass  horizontal  and  place 
the  middle  of  the  cover-glass  on  the  tip 
of  the  ring  finger,  the  watch-crystal 
hanging  below.  The  weight  suspended 
on    the    finger    woukl     be    simj)ly    the    weight    of    the    apparatus. 

3.  Observations.  Place  sufficient  weight  upon  the  watch-glass 
scale-pan  to  nearly  exclude  capillary  circulation  from  the  flattened 
circuhir  area  where  the  cover-glass  presses  upon  the  finger.  If  the 
capillary  circulation  is  completely  excluded  from  this  area  the  skin 


Apparatus  for  determining  the 
capillary  pressure. 


100  SPECIAL  PHYSIOLOGY 

will  look  quite  white.    A  sufficient  weight  should  be  put  on  to  make 
the  area  distinctly  paler,  but  not  white. 

(1)  W\x2it  is  the  diameter  of  the  area  from  which  the  capillary 
circulation  is  excluded? 

(2)  What  is  the  area  expressed  in  square  millimetres? 

(3)  What  weight  was  added  to  the  apparatus? 

(4)  What  is  the  total  weight  resting  on  the  computed  area? 

(5)  What  is  the  weight  in  milligrams  resting  upon  each  square 
millimetre  of  surface? 

(6)  How  high  would  a  column  of  water  be  in  milligrams  that 
would  represent  this  same  pressure  per  square  millimetre? 

(7)  How  high  would  a  column  of  mercury  be  that  would  represent 
this  same  pressure? 

(8)  What  is  the  capillary  pressure  in  the  volar  surface  of  the  ring 
finger  in  the  different  members  of  the  class? 

(9)  Is  the  capillary  pressure  modified  by  a  variation  of  the  position 
of  the  arm? 

(10)  Is  the  capillary  pressure  modified  by  variation  in  the  posture 
of  the  subject:  lying,  sitting,  standing? 

B.   The  Plethy sinograph. 

This  instrument  is  designed  to  determine  the  tissue  pressure 
in  contradistinction  to  the  arterial  pressure  in  larger  arterial 
trunks. 

When  an  arm,  leg,  or  finger  is  thrust  into  a  case  just  large  enough 
to  accommodate  the  member,  any  change  in  the  volume  of  the 
tissues  will  change  the  amount  of  space  between  the  limb  and  the 
case,  and  this  change  in  volume  may  be  easily  traced  with  a  record- 
ing tambour. 

Such  a  case  is  really  a  modified  receiving  tambour  and  is  called  a 
plethysmograph.  One  of  these  adapted  to  the  finger  is  shown  in 
Appendix,  12. 

1.  Appliances.  Plethysmograph;  recording  tambour,  smallest  size 
for  finger,  medium  size  for  arm;  kymograph. 

2.  Preparation.  Pass  the  finger  or  the  bare  arm  through  the 
rubber  collar  of  the  receiver.  The  collar  shoidd  fit  the  arm  above 
the  elbow,  or  the  index  finger  around  the  first  phalanx  tightly  enough 
to  prevent  any  escape  of  air  between  the  tissue  and  collar,  but  not 
tightly  enough  to  prevent  ready  return  of  venous  blood. 

The  tube  leading  from  the  plethysmograph  to  the  recording 
tambour  should  have  a  side  vent,  which  should  be  left  open  while 
the  adjustment  of  the  apparatus  is  in  progress. 

Closing  the  vent,  one  should  find  that  the  tracing  lever  of  the 
recording  tambour  rises  and  falls  rhythmically,  showing  a  rhythmic 
change  in  the  size  of  the  limb. 


THE  CIRCULATION  OF  THE  BLOOD  101 

3.  Observations.  Trace  a  plethysmogram  while  holding  the 
limb  as  still  as  possible.     Breathe  regularly  and  deeply. 

(1)  Are  the  cardiac  contractions  visible  in  the  tracings;  and,  if  so, 
does  the  part  get  larger  or  smaller  in  cardiac  systole? 

(2)  Are  the  respiratory  movements  evident;  and,  if  so,  does  the 
part  get  larger  or  smaller  during  inspiration.    Account  for  results. 

(3)  Wliile  the  arm  is  enclosed  in  the  plethysmograph,  slowly  con- 
tract the  flexor  muscles  of  the  forearm.  Does  the  vohmie  increase 
or  diminish  on  contraction?    Account  for  results. 


XIII.     THE  ACTION  OF  ATROPINE  UPON  THE  HEART. 

1.  Material.  Two  dogs;  atropine  sulphate;  morphine  sulphate; 
chloroform  (or  ether);  mask. 

2.  Preparation.  Make  up  following  solutions:  a  strong  solution 
of  atropine,  0.4  grm.  to  10  c.c;  morphine,  0.6  grm.  to  10  c.c.  Simply 
restrain  dog  "a."  Fasten  dog  "6"  to  board.  Give  hypodermically 
0.03  grm.  of  morphine  to  dog  "6,"  then  anaesthetize  him.  Set  up 
inductorium  so  as  to  obtain  tetanizing  current. 

3.  Experiments  and  Observations.  (1)  Expose  the  vagus  of 
dog  "6."  Stimulate  it  with  weak  induced  current,  using  shielded 
electrode. 

(2)  Count  the  pulse;  then  give  5  mg.  atropine  hypodermically. 

(a)  Count  the  pulse  at  short  intervals  after  the  injection  of  atropine 
for  at  least  thirty  minutes,  or  until  its  rate  is  markedly  affected. 

(6)  What  is  the  effect  of  atropine  on  the  rate  of  the  pulse?  Could 
atropine  produce  this  effect  by  acting  on  the  vagus  centre  ?  On  the 
vagus  fibres?    On  the  heart  muscle  direct? 

(3j  After  the  pulse  rate  has  been  markedly  affected  by  atropine, 
stimulate  vagus  as  before,  using  shielded  electrodes. 

(a)  \Yhat  is  the  effect  on  the  rate  of  the  heart's  action? 

ih)  Compare  this  result  with  that  obtained  in  experiment  (2). 

(c)  Had  atropine  acted  solely  by  depressing  the  vagus  centre,  would 
we  have  found  a  difference  in  results  in  stimulating  the  vagus  nerve 
before  and  after  its  exhibition? 

(d)  Had  atropine  acted  on  the  accelerator  apparatus,  would  there 
be  a  difference  in  such  results? 

(e)  If  now,  on  stimulating  the  heart  muscle  directly,  you  obtained 
a  normal  physiological  effect,  to  what  elements  have  you  limited  the 
possible  action  of  atropine? 

ij)  Basing  your  opinion  on  the  experiments  you  have  performed, 
to  what  elements  have  you  limited  the  possible  action  of  atropine? 

(4)  Further  general  observations. 

{a)  Note  condition  of  visible  mucous  membranes  with  regard  to 
their  secretions. 

ih)  If  dog  can  be  kept  until  next  day,  note  size  of  pupils. 


102  SPECIAL  PHYSIOLOGY 

XIV.     THE  ACTION  OF  PILOCARPINE  UPON  THE  HEART. 

1.  Material.  One  rabbit;  one  dog;  hydrochlorate  of  pilocarpine; 
sulphate  of  morphine;  sulphate  of  atropine;  chloroform. 

2.  Preparation.  Make  solution  of  pilocarpine,  50  grm.  to  10  c.c. ; 
atropine,  0.02  grm.  to  10  c.c;  morphine,  0.6  to  10  c.c. 

Do  not  fasten  the  rabbit  to  the  holder.  Fasten  the  dog  to  the 
dog  board,  after  giving  preliminary  hypodermic  injection  of  0.03 
grm.  of  morphine. 

3.  Experiments  and  Observations.  (1)  Give,  hypodermically, 
5  mg.  per  kg.  pilocarpine  to  rabbit.  Record  weight,  pulse,  and  tem- 
perature.    Note  secretions  and  size  of  pupils. 

(a)  Record  symptoms  as  they  arise,  especially  as  regards: 
(I)  Secretions. 
(II)  Pulse  rate. 

(III)  Size  of  pupil. 

(IV)  Temperature. 
(V)   Weight. 

(6)  Formulate  the  total  effect  of  pilocarpine  upon  the  animal. 

(2)  After  morphinizing  the  dog,  fasten  it  firmly  to  the  dog  board 
and  lightly  anaesthetize;  expose  both  vagi.  Count  the  pulse.  Give 
a  subcutaneous  injection  of  0.03  grm.  pilocarpine.  After  salivation 
has  become  profuse  count  the  pulse  again. 

How  does  pilocarpine  affect  the  pulse  rate? 

(3)  Now  sever  the  vagi. 

(a)  How  does  the  severing  of  the  vagi  affect  the  normal  animal? 

(6)  How  does  it  affect  an  animal  poisoned  by  pilocarpine? 

(c)  Could  pilocarpine  alter  the  effect  produced  by  severing  vagi 
if  it  acted  on  the  proximal  side  of  the  point  at  which  the  vagi  were 
cut?    On  a  point  beyond  that  at  which  they  were  cut? 

{d)  Could  the  pilocarpine  alter  the  effect  normally  produced  by 
severing  the  vagi,  by  acting  on  the  cardiac  sympathetic? 

(e)  Enumerate  the  possible  points  at  which  pilocarpine  may  act 
to  produce  the  effects  observed. 

(4)  Give  the  same  dog  5  mg.  atropine,  hypodermically. 
(a)  Is  the  rate  of  heart  beat  altered? 

(6)  Where  does  atropine  act  to  produce  alteration  in  rate  of  heart 
beat? 

(c)  Does  atropine  antagonize  the  action  of  pilocarpine  in  this 
experiment  ? 

{d)  To  what  elements  have  you  limited  the  probable  action  of 
pilocarpine  ? 

(5)  General  observations. 

(a)  Compare  the  action  of  pilocarpine  with  that  of  atropine 
throughout  the  range  of  action  observed. 

(6)  Is  atropine  a  physiological  antagonist  of  pilocarpine? 


THE  CIRCULATION  OF  THE  BLOOD  103 

XV.     THE  ACTION  OF  DIGITALIS  UPON  THE   HEART. 

1.  Material.  Tincture  digitalis;  sulphate  of  morphine;  sodic 
chloride;  chloroform;  two  dogs;  one  frog;  sodic  carbonate  (one-half 
saturated  solution). 

2.  Preparation.  Make  solution  of  morphine,  0.6  grm.  to  10  c.c. 
Pith  frog.  Morphinize  dogs,  using  0.03  grm.,  and  chloroform  them 
pre\'ious  to  operation.  Set  up  induction  coil  so  as  to  obtain  tetanizing 
current,  having  contact  key  in  primary  circuit.  Prepare  kymograph 
for  tracing. 

3.  Experiments  and  Observations.  (1)  Fasten  a  dog  firmly  to 
the  dog  board  and  lightly  anaesthetize.  Expose  the  vagus.  Count 
the  pulse.  Using  shielded  electrodes  and  separating  secondary  from 
primary  coil,  find  a  current  just  weak  enough  not  to  affect  heart 
when  applied  to  vagus.  Now  inject  subcutaneously  0.3  c.c.  tincture 
digitalis  per  kilo  animal.  After  waiting  at  least  twenty  minutes,  in 
the  mean  time  using  no  anaesthetic  except  a  repetition  of  the  morphine 
if  necessary,  and  keeping  the  wound  closed  after  moistening  with 
saline  solution,  stimulate  the  vagus  with  same  current  that  before 
the  exhibition  of  digitalis  was  unable  to  affect  the  heart. 

(a)  What  is  the  function  of  the  cardiac  fibres  of  the  vagus? 

(6)  What  result  is  produced  by  the  stimulation  of  these  fibres 
in  the  normal  animal? 

(c)  Does  digitalis  increase  or  decrease  the  influence  of  the  vagus? 
(Maximum  effect  occurs  after  two  hours.) 

{d)  With  the  stimulus  applied  to  the  vagus  fibres,  the  cardiac 
fibres  carrying  impulses  centrifugally,  could  this  altered  excitability 
be  due  to  central  action  of  the  digitalis? 

(2)  After  morphinizing  dog,  fasten  firmly  to  dog  board  and  Hghtly 
anaesthetize;  expose  carotid  artery. 

Insert  the  cannula  of  the  manometer  tambour  apparatus  into 
the  artery.  There  must  be  no  air-bubbles  in  the  apparatus  at  any 
point. 

The  anaesthetic  should  be  discontinued  as  soon  as  the  cannula  is 
in.serted  into  the  artery.  Take  normal  tracing  and  read  pressure  as 
indicated  in  the  manometer.  Now  give  the  dog,  hypodermically, 
0.3  c.c.  tincture  digitalis  for  each  kilo  of  weight. 

(a)  Watch  effect  on  elevation  of  mercury  meniscus,  making 
tracings  at  short  intervals. 

(b)  What  factors  enter  into  arterial  pressure? 

{(:)  How  does  a  "high-pressure"  tracing  differ  from  a  "low- 
pressure"  tracing? 

id)  What  effect  has  digitahs  on  arterial  pressure? 

('3j  Having  firmly  fastened  a  pithed  frog  to  frog  board  with  web 
stretchcfl  over  a  hole  in  the  board,  focus  the  microscope  upon  a 
certain  arteriole  in  the  field,  and  measure  its  fliameter  with   an  eye- 


104  SPECIAL  PHYSIOLOGY 

piece  micrometer.  Now  inject  into  dorsal  lymph  spaces  0.3  c.c. 
tincture  digitalis  and  measure  same  arteriole  at  intervals  of  ten 
minutes.     Keep  the  web  moist  with  normal  saline  solution. 

(a)  What  change  occurs  in  the  diameter  of  the  arteriole? 

(6)  What  effect  would  you  expect  this  to  have  on  arterial  pressure  ? 

(c)  Would  its  action  on  the  arterioles  help  to  account  for  its  effect 
on  arterial  pressure? 

(4)  Comparisons.  Compare  digitalis  and  atropine  with  regard  to 
(a)  their  effects  on  the  rate  of  the  heart  beat;  (6)  their  effects  on  the 
irritability  of  the  vagus. 


XVI.    THE  ACTION  OF  ACONITE  UPON  THE  CIRCULATION. 

1.  Material.  Tincture  aconite;  sulphate  of  atropine;  one  dog; 
one  frog;  sphygmograph. 

2.  Preparation.  Make  solution  of  atropine,  0,02  grm.  to  10  c.c. 
Pith  frog.     Do  not  fasten  the  dog  to  dog  board. 

3.  Experiments  and  Observations.  (1)  Give  1  c.c.  tincture 
aconite  hypodermically  to  the  dog.  Record  symptoms  as  they  arise. 
(1  c.c.  often  not  fatal.) 

(2)  Fasten  the  pithed  frog  on  its  back  to  the  board.  Count  the 
heart  beats,  exposing  heart  if  necessary.  Now  give  two  drops  tincture 
aconite  subcutaneously.  What  effect  has  aconite  on  the  pulse  rate? 
(To  obtain  satisfactory  results,  observations  must  be  made  at  short 
intervals,  for  from  thirty  to  sixty  minutes.) 

(3)  Take  a  sphygmographic  tracing  of  the  radial  pulse  of  a  student. 
Note  the  pulse  rate.  Administer  by  mouth  0.2  c.c.  tincture  aconite 
and  0.06  c.c.  every  ten  minutes  until  action  on  pulse  is  noticeable. 
Repeat  tracing  and  counting  of  pulse  at  short  intervals. 

(a)  How  does  aconite  affect  blood  pressure? 

(6)  How  is  the  rate  of  the  heart's  action  affected? 

(c)  What  subjective  sensations  are  produced? 

(4)  Comparisons.  Compare  aconite  and  pilocarpine  with  regard 
to  their  action  on  the  gastrointestinal  system. 


XVII.  THE  ACTION  OF  ADRENALIN   UPON  THE  CIRCULATION. 

1.  Materials.     White  rabbit;  adrenahn. 

2.  Preparation.  Make  solution  of  adrenalin  0.01  grm.  to  10  c.c. 
of  normal  saHne  solution.  Weigh  the  rabbit  and  fasten  it  to  the 
holder,  and  with  probang  made  of  absorbent  cotton  on  probe  apply 
solution  to  cornea;  note  local  effect  on  peripheral  circulation. 

3.  Operation.  Anaesthetize  rabbit,  expose  carotid,  and  insert 
cannula  into  artery  and  take  blood  pressure.    Ligate  external  carotid; 


THE  CIRCULATION  OF  THE  BLOOD  105 

inject  toward  heart  enough  of  the  sohition  to  make  2  grm.  per  kilo 
animal;  ligate  below  needle  point  and  withdraw  needle. 

4.  Observations.     (1)  What  is  the   effect   of   adrenalin   applied 
locally  ? 

(2)  What  is  the  effect  upon  the  peripheral  circulation  of  adrenalin 
injected  intravenously  ? 

(3)  Is  the  rate  or  apparent  force  of  the  heart  modified  by  adrenaUn? 

(4)  Is  the  blood  pressure  modified;  if  so,  how  may  the  change 
be  accounted  for? 


CHAPTER   IV. 


EESPIRATION. 

I.  THORACIC   MOVEMENTS.       INTRATHORACIC   PRESSURE. 

1.  Appliances  necessary  for  these  exercises  are:  Kymograph; 
physiological  operating  case;  clippers;  stethograph;  thoracic  cannula. 
(See  Appendix,  12.)  The  stethograph  consists  of  two  tambours; 
the  recording  tambour  is  the  same  as  used  in  other  analogous 
experiments  (Fig.  56),  while  the  receiving  tambour,  joined  to 
the  recording  tambour  through  a  ^-inetre  length  of  No.  ^  pressure 
tubing,  is  provided  with  a  cork  button  which  may  be  placed  upon 
the  rabbit's  thorax  and  receive  and  communicate  its  movements  to 
the  air  in  the  tambour  system. 

Fig.  56 


Recording  tambour.    (Described  in  Appendix,  12.) 

2.  To  Study  the  Movements  of  the  Rabbit's  Thorax.    The 

problem  is  to  take  a  graphic  tracing  or  stethogram  of  the  movements 
of  the  thoracic  walls,  and  from  this  tracing  to  determine  the  rate 
and  the  character  of  the  movements,  particularly  the  latter. 

To  record  a  stethogram,  fasten  the  rabbit  upon  its  board  and  hold 
the  button  of  the  receiving  tambour  upon  the  thorax,  tracing  the 
movement  of  the  lever  upon  the  kymograph. 

Study  the  characteristics  of  this  curve. 

Anaesthetize  the  rabbit  with  ether.  How  does  the  stethogram  vary 
as  the  anaesthesia  progresses?  Is  the  stethogram  of  full  anaesthesia 
different  in  any  essential  feature  from  the  normal  one? 


RESPIRA  TION  \  07 

3.  To  Study  the  Intrathoracic  Pressure.  Locate  an  intercostal 
space  to  the  right  of  the  sternum  and  opposite  its  middle  point. 
]\Iake  an  incision  1  cm.  long,  parallel  with  the  intercostal  space  and 

1  cm.  from  the  sternum.  Dissect  through  the  intercostal  muscles, 
taking  care  not  to  cut  the  pleura.  Insert  into  the  wound  the  point 
of  the  glass  cannula,  previously  provided  with  a  rubber  tube  which 
is  clamped,  and  press  it  carefully  through  the  pleura  into  the  right 
pleural  cavity. 

Join  the  rubber  tube  to  a  recording  tambour  and  unclamp.  Slowly 
and  gently  manipulate  the  cannula  until  there  is  evident  communica- 
tion through  the  lumen  of  the  cannula  and  tube  from  the  pleural 
cavity  to  the  tambour. 

So  adjust  the  cannula  that  the  recording  lever  makes  the  maximum 
excursion.  Bring  the  levers  into  such  a  relation  to  the  kymograph 
that  the  tracing  point  of  the  stethograph  lever  shall  be  vertically 
over  that  of  the  lever  which  is  to  record  intrathoracic  pressure,  and 

2  cm.  to  3  cm.  from  it. 

Trace  upon  the  drum  a  stethogram  and  chronogram  as  well  as 
an  intrathoracic  pressure  record,  taking  care  that  the  tracing  points 
of  the  recording  tambours  are  in  a  vertical  line. 

(1)  Does  the  rhythm  of  varying  pressure  correspond  to  the  rhythm 
of  the  respiratory  movements? 

(2)  If  so,  does  that  necessarily  establish  between  them  the  relation 
of  cause  and  effect? 

(3)  What  change  of  pressure  is  indicated  by  the  rise  of  the  pressure 
lever? 

(4)  What  movement  of  the  pressure  lever  corresponds  to  a  rise 
of  the  stethograph  lever? 

(5)  What  is  the  condition  of  intrathoracic  pressure  during  inspira- 
tion?    During  expiration? 

(6)  Stop  the  entrance  of  the  air  into  the  respiratory  passages  by 
closing  the  rabbit's  nostrils.  What  effect  does  this  have  upon  the 
respiratory  movements  ? 

(7j  Is  the  intrathoracic  pressure  affected  by  the  experiment?  If 
so,  explain  the  effect. 

(8j  If  two  phenomena  correspond  perfectly  in  their  cycles,  and  if 
a  variation  of  one  is  always  accompanied  by  a  variation  in  the  other, 
can  there  be  any  reasonable  doubt  that  they  sustain  to  each  other 
the  relation  of  cause  and  effect? 

(9)  Is  one  of  the  phenomena  in  question  the  cause  of  the  other? 
If  so,  state  which  is  the  cause  and  estaljlish  your  position. 

(10 J  Clamp  the  rubber  tube  of  the  pressure  apparatus.  Replace 
the  recording  tambour  with  a  water  manometer.  Unclamp.  Is  the 
pressure  during  inspiration  positive  or  negative,  and  how  much? 

(11)  Is  the  pressure  during  expiration  positive  or  negative,  and 
how  mnch? 


108 


SPECIAL  PHYSIOLOGY 


(12)  If  the  whole  apparatus  were  filled  with  water  instead  of  air 
and  water,  would  it  make  any  essential  difference  in  the  result? 
What  effect  do  the  variations  of  the  intrathoracic  pressure  have 
upon  the  circulation? 


II.  RESPIRATORY    PRESSURE.      ELASTICITY    OF    THE    LUNGS. 
PNEUMATOGRAM. 

A.  Respiratory  Pressure. 

1.  Appliances.  Operating  case;  clippers;  rabbit  board;  ether; 
ether  cone;  absorbent  cotton;  rabbit  stethograph;  kymograph;  a 
small  mercury  manometer,  to  the  proximal  limb  of  which  is  attached 
a  thick-walled  rubber  tube,  a  piece  of  glass  tubing  for  a  mouth-piece, 
a  screw  clamp;  chronograph;  two  recording  tambours;  rabbit. 

2.  Preparation.  Fix  the  rabbit  to  the  operating  board  and  anaes- 
thetize; clip  the  ventral  surface  of  the  neck.  Join  up  the  manometer 
as  shown  below. 

Fig.  57 


Tracheal  cannula,  with  manometer  attached. 


3.  Operation.  Make  a  longitudinal  incision  over  the  trachea, 
through  skin  and  connective  tissue.  Part  the  sternothyroid  muscles 
in  the  median  line  and  expose  the  trachea.  Separate  the  trachea 
from  the  oesophagus  and  other  surrounding  tissue's  for  3  cm.  below 
the  larynx.  Carefully  pass  a  strong  linen  ligature  under  the  trachea. 
Make  a  median  ventral  slit  in  the  trachea  anterior  to  the  ligature. 
Pass  through  the  slit  the  limb  of  the  Y-tube  marked  /  (Fig.  57). 
Ligate. 

4.  Observations.  Respiratory  Pressure.  The  Pneumatogram.  (1) 
After  the  ligature  is  tied  how  does   the   rabbit   breathe?    Are  the 


RESPIRATION  109 

thoracic  and  abdominal  movements  of  respiration  accompanied   by 
other  respiratory  movements  ? 

(2)  With  tube  N  (Fig.  57)  open,  is  there  any  variation  of  the 
mercury  during  respiration? 

(3)  With  a  screw  clamp  slowly  close  tube  N.  As  the  resistance  to 
the  flow  of  air  increases,  what  change  is  noted  in  the  manometer? 

(4)  Quickly  clamp  tube  N  at  end  of  expiration  and  carefully  note 
the  manometer  reading.     Is  it  positive  or  negative? 

(5)  Clamp  tube  N  at  the  end  of  inspiration.  Is  the  pressure  posi- 
tive or  negative? 

(6)  You  have  been  determining  certain  facts  regarding  respiratory 
pressure.  Are  the  causes  of  the  changes  of  respiratory  pressure  the 
same  as  the  causes  of  the  changes  of  intrathoracic  pressure? 

(7)  In  what  way  does  respiratory  pressure  differ  from  intra- 
thoracic pressure? 

(8)  Disjoin  the  manometer  and  join  its  tube  to  a  recording  tambour 
and  trace  a  pneumatogram,  with  stethogram  and  chronogram. 

(9)  Compare  the  pneumatogram  with  the  tracing  of  intrathoracic 
pressure.     Account  for  all  differences. 

(10)  While  dispatching  the  rabbit  with  chloroform  trace  a  pneu- 
matogram of  chloroform  narcosis.  Describe  its  characteristics. 
Does  the  heart  continue  to  beat  after  the  respiration  has  ceased? 

B.  Elasticity  of  the  Rabbit's  Lungs. 

(1)  After  the  death  of  the  rabbit  open  the  thorax  freely,  taking 
care  not  to  wound  the  visceral  pleura.  The  lungs  will  collapse.  Why  ? 

(2)  Replace  the  manometer;  gently  blow  into  the  mouth-piece  until 
the  lungs  have  been  inflated  to  their  normal  size.  Measure  carefully 
the  rise  of  mercury  in  the  distal  column.  What  degree  of 
positive  respiratory  pressure  will  the  elasticity  of  the  lungs  alone 
cause  ? 

(3)  What  is  the  significance  of  the  elasticity  of  the  lungs  in  respi- 
ration ? 

C.  The  Cardio-pneumatogram. 

Remove  the  tube  A^  from  the  Y-tube;  join  it  to  a  recording  tambour. 

(Ij  Let  a  member  of  a  division  sit  in  perfect  repose,  and,  while 
the  drum  of  the  kymograph  rotates  very  slowly,  hold  the  mouth- 
piece between  the  lips.  Hold  the  nose  and  suspend  all  respiratory 
movements  for  a  period.  Let  some  member  of  the  division  count 
the  pulse  of  the  experimenter.     Trace  the  cardio-pneuinatograni. 

(2)  Is  there  a  relation  between  the  rhythm  of  tiie  pulse  and  the 
waves  of  the  tracing?    If  so,  account  for  this  relation. 

(3j  Account  U)V  the  essential  features  of  the  cardi()-f)n('nmatogram. 


110 


SPECIAL  PHYSIOL OG  Y 


III.   TO  STUDY  THE  MOVEMENTS  OF  THE  HUMAN  THORAX. 

1.  Appliances.  Stethograph  (see  Appendix,  14);  chest  pantagraph 
(see  Appendix,  15) ;  chronograph  and  kymograph. 

2.  Observations.  With  the  stethograph  (Fig.  58).  (1)  How 
much  may  be  learned  of  man's  respiratory  movements  by  simple 
inspection?     Make  a  careful  enumeration  and  record. 


Fig.  58 


The  human  stethograph :  St,  stand  with  heavy  base,  supporting  a  thoracic  frame  constructed 
of  gas-pipes  and  clamps  ;  a  and  a',  horizontal  parallel  arms,  to  he  adjusted  on  either  side  of  the 
thorax ;  a',  to  touch  the  thoracic  wall ;  RT,  receiving  tambour,  constructed  as  described  in  the 
Appendix ;  the  movements  of  the  cork  c,  which  touches  the  thoracic  wall,  are  transmitted  to  the 
recording  tambour  rt,  thence  traced  on  the  kymograph  K. 


(2)  Take  a  stethogram  of   the   lateral   diameter   in   the  nipple 
plane. 

(3)  Take  a  stethogram  of  the  dorsoventral  diameter  of  the  thorax 
over  the  middle  of  the  sternum  in  the  nipple  plane.     Compare. 

(4)  Adjust  the  stethograph  and  make  a  record  (a  stethogram)  of 
the  changes  of  the  lateral  diameter  of  the  thorax  at  the  ninth  rib. 


RESPIRATIOX 


111 


(5)  Take  a  lateral  ninth-rib  stethogram  while  the  subject  reads  a 
paragraph,  sighs,  coughs,  and  laughs.    Account  for  the  peculiarities. 

(6)  Take  a  lateral  ninth-rib  stethogram  after  the  subject  has 
taken  vigorous  exercise.     What  changes  are  to  be  noted? 

(7)  Compare  the  stethogram  from  several  individuals.  Determine 
the  essential  features  and  give  causes  of  these. 

(8)  Seek  the  causes  of  the  differences  which  exist  between  stetho- 
grams  of  different  individuals.  INIay  they  be  accounted  for  by 
stature,  condition,  occupation,  or  habit? 

3.  Observations.  With  the  chest  pantagraph.  The  purpose  of 
this  instrument  is  to  record  the  outline  of  any  horizontal  section  of 
the  thorax,  though  it  could  be  used  as  well  for  tracing  the  periphera 

Fig.  59 


The  chest  pantagraph.  For  measuring  and  recording  chest  contours.  The  instrument  is 
constructed  of  brass  or  of  wood  with  brass  or  steel  semicircle.  The  joints  a,  b,  x,  and  y  move 
easily  in  the  plane  of  the  instrument.  The  semicircle,  forty  inches  in  diameter,  rotates  at  x 
around  the  diameter  t  x.  The  point/is  fixed  to  a  table.  With/  a  fixed  point  all  movements  of  t, 
the  tracing  point,  are  accompanied  by  corresponding  movements  of  r,  the  recording  point.  The 
triangle/  r  b  and  ft  a  are  similar  triangles  in  all  positions  of  the  instrument  fb:/a  :  :  f  r  :  f  t ; 


but  f-  =  .'<  therefore  the  distance/ r  is  always  ' 


the  distance/^. 


of  the  abdomen,  of  the  head,  or  of  the  limb.  To  use  the  pantagraph 
for  the  purpose  here  intended,  let  the  subject  sit  beside  a  table  adjust- 
able as  to  height.  Make  such  adjustment  as  to  bring  the  circum- 
ference of  the  thorax  to  be  observed  even  with  the  upper  surface  of 
the  table.  Fix  the  point  /  of  the  instrument  to  the  table.  Let  the  ob- 
.server  locate,  with  pen  or  pencil,  upon  the  side  of  the  subject  distal  from 
the  table,  a  point  which  shall  serve  as  a  starting  point.  (See  Fig.  59.) 
When  the  point  (/)  of  the  instrument  rests  upon  this  point  of  the 
subject's  thorax  the  instrument  should  be  well  extended,  somewhat 
more  than  represented  in  the  figure.  Fix  a  sheet  of  paper  to  the 
table  under  the  recording  pencil  at  r.  To  take  a  graphic  record  of 
the  contf)ur  of  the  thorax  proceed  as  follows: 


112 


SPECIAL  PHYSIOLOGY 


(a)  Let  the  observer  place  the  tracing  point  {t)  upon  the  "starting 
point"  on  the  distal  side  of  the  thoracic  perimeter. 

(h)  Sweep  the  tracing  point  quickly  around  one-half  the  perimeter 
to  a  point  approximately  opposite  to  the  starting  point. 

(c)  Rotate  the  curved  arm  of  the  instrument  upon  its  axis  {t  x) 
through  180  degrees. 


Fig.  60 


Fig.  61 


Fig.  60.— The  water  spirometer.     The  outer  receptacle  contains  water.     The  inner  inverted 
reservoir  receives  the  air  through  the  mouth  tube,  at  the  right,  and  is  raised. 
Fig.  61. — Pneomanometer. 


{d)  Sweep  the  tracing  point  around  the  other  one-half  of  the 
perimeter  to  the  starting  point. 

The  movements  of  the  tracing  point  {i)  in  the  horizontal  plane  have 
been  faithfully  recorded  upon  the  sheet  of  paper  by  the  recording 
pencil  at  r.  It  is  hardly  necessary  to  remind  the  student  that  the 
subject  must  remain  motionless  during  the  observation. 


I 


R  ESP  IE  A  TION  113 

d)  Take  a  thoracic  perimeter  with  the  chest  in  repose.  Measure 
different  diameters  of  the  tracing  and  muhiply  bv  five  to  reduce  to 
actual  measurements. 

(2)  Take  a  tracing  at  end  of  forced  expiration;  at  end  of  forced 
inspiration.     Compare  diameters. 

(3)  Make  a  series  of  these .  tracings  for  different  individuals. 
Compare. 

(4)  Do  different  individuals  of  the  class  represent  different  types 
of  contour,  as  broad,  medium,  and  deep? 

(5)  Which  t^'pe  of  chest  is  capable  of  adding  the  greatest  area 
of  contour  by  expansion? 


IV.    LUNG   CAPACITY   i  CHEST  MEASUREMENTS,  RESPIRATORY 
PRESSURE  .     RECORDING  OF  ANTHROPOMETRIC   DATA. 

1.  Instnunents.  Spirometer  (Fig.  60);  pneoraanometer  (Fig.  61); 
meter  tape;  steel  calipers;  standard,  with  horizontal  arm  for  meas- 
uring height;  scales  for  taking  weight. 

2.  Observations.  (1)  Test  with  spirometer  the  lung  capacity 
of  each  member  of  the  division.  May  differences  in  lung  capacity 
be  accounted  for  by  difference  in  stature,  condition,  occupation,  or 
habit? 

(2)  Take  with  the  meter  tape  the  girth  of  chest  over  the  nipples 
in  a  plane  at  right  angles  with  the  axis  of  the  thorax. 

(a)  AVith  chest  in  normal  repose. 

(b)  At  the  end  of  forced  expiration. 

(c)  At  the  end  of  forced  inspiration. 

(3j  Take  the  girth  of  chest  over  the  juncture  of  the  ninth  rib  with 
its  cartilage,  holding  the  tape  in  a  plane  at  right  angles  with  the  axis 
of  the  thorax. 

(a)  With  the  chest  in  repose. 

(6)  At  the  end  of  forced  expiration, 
(c)  At  the  end  of  forced  inspiration. 

(4)  With  the  calipers  measure  the  dorsoventral  diameter  at  the 
level  of  the  nipple,  holding  the  calipers  in  a  plane  perpendicular  to 
the  axis  of  the  thorax. 

(a)  Normal ;  (b)  after  forced  expiration ;  (c)  after  forced  in.spiration. 

(5)  Take  the  lateral  diameter  in  the  nipple  plane. 

(a)  Normal;  (b)  after  forced  expiration;  (c)  after  forced  inspiration, 

(fj)  Take  the  lateral  diameter  at  the  ninth  ril). 

(a)  Normal;  (b)  after  forced  expiration;  (cj  after  forced  inspiration. 

(7)  Test  with  pneomanometer  the  force  of  inspiration  and  expira- 
tion. IvCt  each  member  of  the  division  test  with  the  pneomanometer 
the  maximum  positive  pressure  which  he  is  able  to  produce  in  the 
respiratory  passages  during  expiration. 

8 


114  SPECIAL  PHYSIOLOGY 

(8)  Test  with  the  same  instrument  the  maximum  negative  pressure 
which  each  individual  can  produce  during  inspiration. 

(9)  Does  the  face  become  red  in  either  of  these  tests?  If  such 
is  uniformly  observed,  account  for  it. 

(10)  The  preservation  of  data.  Experience  has  shown  that  when 
data  are  to  be  preserved  for  subsequent  use  in  comparison  of  one 
class  of  individuals  or  cases  with  another,  it  is  very  much  more 
economical  in  time  to  record  the  data  upon  cards. 

For  the  above  data  one  may  use  such  a  card  as  is  appended  below. 

In  addition  to  the  measurements  above  given  record  upon  the 
cards  the  weight,  the  height,  the  bodily  condition  of  the  individual, 
and  especially  whether  the  individual  has  lived  in  a  hilly  or  in  a 
flat  country,  and  whether  he  has  been  active  or  inactive. 


Name ...       Address 

Place  of  residence :  level,  hilly,  or  mountainous  altitude 


Previous  occupation 

Habits:  Exercise,  sports,  character,  amount 


f  Father's  weight height 

Parents  -{ 

[  Mother's  weight height 

Which  parent  do  you  resemble  physically  ? 

Which  parent  do  you  resemble  temperamentally  ?      .      .      .      . 


Age Weight  ....      Emaciated,  thin,  spare,  stout,  obese- 
Height   ....     Dwarfish,  short,  medium,  tall,  very  tall, 

r  Inspiration 

Lung  capacity  ....     Respiratory  pressure  ^ 

[Expiration 


Girth  of  Chest,  Nipple  Plane: 

1.  Repose    ...       2.  Inspiration     .      .      .      .3.  Expiration 
4.  Expansion Per  cent 

Diameter  of  Chest,  Dorsoventral : 

1.  Repose    ...        2.  Inspiration     .      .      .      .3.  Expiration 
4.  Expansion Per  cent 

Diameter  of  Chest,  Lateral: 

1-  Repose    ...       2.  Inspiration   ....     3.   Expiration 

4.  Expansion Per  cent 

Examiner 

Date 


EESFIEATION  II5 

V.    THE   EVALUATION   OF   ANTHROPOMETRIC   DATA. 

A  large  proportion  of  the  problems  that  the  medical  man  has  to 
solve  involves  the  finding  of  averages  of  a  large  number  of  observa- 
tions. This  is  sure  to  be  true  in  all  anthropometric  problems.  In 
the  course  of  the  preceding  lesson  valuable  anthropometric  data 
were  collected  and  recorded  upon  cards.  The  value  of  this  material 
is  purely  potential.  Before  the  data  will  furnish  a  basis  for  drawing 
conclusions  it  is  necessary  to  subject  them  to  a  process  of  evaluation. 
This  process  consists,  first,  in  grouping;  second,  in  getting  the  average 
or  the  median  value  for  each  measurement;  and,  third,  in  graphically 
representing  the  averages.  In  the  previous  lesson  the  observer  noted 
upon  each  card  whether  the  subject  had  lived  in  a  hilly  or  flat  country; 
further,  whether  he  had  lived  a  physically  active  or  inactive  life. 
This  gives  one  an  opportunity  for  four  groups  when  the  cards  for 
the  whole  class  are  collected. 

Group      I.     Active  men  from  a  hilly  country. 

Group    II.     Active  men  from  a  flat  country. 

Group  III.     Inactive  men  from  a  hilly  country. 

Group  IV.  Inactive  men  from  a  flat  country. 
Until  recently  it  has  been  customary  simply  to  write  the  data  for 
any  group  in  columns  and  ''strike  an  average"  of  each  column. 
If  there  are  only  10  to  20  or  30  individuals  in  each  group  this  method 
does  not  entail  the  unnecessary  expenditure  of  much  energy,  but  it 
is  not  reliable,  for  one  "giant"  or  "dwarf"  in  any  group  would 
vitiate  the  whole  result.  If  there  are  100  or  1000  individuals  in  a 
group,  then  the  use  of  the  old  method  of  finding  the  arithmetical 
average  is  exceedingly  wasteful  of  both  time  and  energy.  It  must 
be  arlded,  however,  that  when  the  number  of  observations  is  large 
the  chances  are  that  there  will  be  as  many  dwarfs  as  giants,  thus 
making  the  average  approximate  closely  the  median  value.  It  is 
the  latter  we  are  seeking,  viz.,  the  median  value;  this  may  be  defined 
as  that  value  which  is  so  located  in  the  whole  series  of  observations 
in  a  single  measurement  of  any  group,  that  there  are  as  many  below 
it  as  above  it — i.  e.,  that  the  number  of  values  which  it  exceeds  equals 
the  number  of  values  which  exceed  it. 

Let  us  take  a  concrete  case.  In  a  group  of  316  seventeen-year-old 
boys  certain  physical  measurements  were  recorded  upon  individual 
canis.  Let  us  take,  for  example,  the  girth  of  the  head  recorded  in 
centimetres  and  tenths.  Instead  of  writing  in  a  column  the  316 
head-girths,  each  expressed  in  three  figures,  adchng  and  averaging, 
let  us  adoj^t  the  new  method,  first  suggested  by  the  Belgian  astronomer 
and  anthropologist,  Quetelet,  and  later  elaborated  by  Galten,  the 
London  anthnjpologist.  Arrange  the  cards  in  piles,  placing  in  one 
pile  all  (;f  the  cards  having  girth  of  head  51  cm.,  in  another  pile  all 


116 


SPECIAL  PHYSIOLOGY 


having  52  cm.,  and  so  on.  In  the  case  in  question  it  was  found  that 
the  316  cards  were  quickly  distributed,  falhng  into  the  following 
groups : 


Girth  of  head      . 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

No.  of  observations    . 
(i.  e.,  of  cards.) 

1 

7 

17 

41 

70 

74 

60 

29 

10 

7 

The  problem  is  to  find  the  value  of  the  median  measurement  or 
the  median  value.  There  are  158  values  below  the  median  value 
and  as  many  above  it. 

1.  To  Locate  the  Median  Observation.  This  is  equivalent  to  saying 
— find  in  the  lower  series  of  numbers  (1-7-17,  etc.)  the  158th  observa- 
tion from  either  end.  It  must  be  located  in  the  pile  of  cards  which 
number  74.  This  group  may  be  called  the  median  group.  But  where 
in  this  group  is  the  median  observation  located  ?  In  order  to  deter- 
mine this,  add  the  groups  to  the  left  of  the  median  group,  these  may 
be  called  the  minus  groups,  the  values  which  they  represent  being 
less  than  that  of  the  median  group:  1,  7,  17,  41,  70  =  136. 

To  this  sum  we  must  add  22  observations  from  the  median  group 
to  make  158.  The  median  observation  is  then  located  in  the  median 
group,  22  points  from  the  left. 

2.  To  evaluate  the  median  observation  we  must  take  it  for  granted 

that  the  74  observations  of  the  median  group  are  evenly  distributed 

over  the  distance  between  56  cm.  and  57  cm.    That  being  the  case, 

22 
the  median  value  would  be  56  and  jtt  cm. 

74 

If  it  is  desired  to  reduce  this  simple  process  to  a  mathematical 

formula,  that  can  readily  be  done: 

Let  w=the  total  number  of  observations  (316). 

m=the  number  of  observations  in  the  median  group  (74), 

Z=the  sum  of  the  minus  groups  at  the  left  (136). 

r  =  the  sum  of  the  plus  groups  to  the  right  (106). 

a=the  minimum  value  of  the  median  group  (56  cm.). 

d=ihe  arithmetical   difference  in  the  minimum  values  of 

the  groups  (1  cm.). 

M=the  median  value  to  be  determined. 


Then  M  =  a-i- 


Kl-') 


or  M- 


/316 

56+^\  2 


-  — ISe)       -„22 
74 


56.3  cm. 


After  one  has  found  the  median  value  for  each  measurement  in 
each  group,  these  may  be  tabulated  and  the  values  compared.  When 
the  table  of  median  values  is  large  it  is  almost  necessary  to  carry  the 
work  of  reduction  a  step  farther  and  represent  these  values  graphic- 


RESPIRATION 


117 


ally  in  a  chart.  Another  opportunity  will  be  used  for  giving  the 
methods  used  in  the  graphic  representation  of  statistical  tables. 

The  table  which  results  from  the  data  collected  in  connection  with 
the  previous  lesson  is  not  so  large  but  that  the  observer  can  practi- 
cally comprehend  the  whole  at  a  glance. 

Our  grouping  enables  us  to  answer  the  following  questions : 

1.  Has  general  physical  activity  any  essential  influence  in  the 
development  of  the  respiratory  organs  and  function? 

2.  Is  the  climbing  of  hills  in  early  life  a  factor  in  the  development 
of  the  respiratory  organs  and  function? 

If  both  of  these  questions  may  be  answered  affirmatively,  then 
one  would  expect  to  find  that  the  median  values  of  Group  I.  (active 
individuals  from  a  hilly  country)  uniformly  exceed  the  values  of 
Group  II.,  and  that  those  of  Group  III.  uniformly  exceed  those  of 
Group  IV.,  but  that  the  median  lines  of  Group  II.  may  or  may  not 
exceed  those  of  Group  III. 


VI.    QUANTITATIVE    DETERMINATION    OF    THE    COj  AND   H^O 
ELIMINATED  FROM  AN  ANIMAL'S  LUNGS  IN 
A  GIVEN  TIME. 

1.  Appliances.     A  4-ounce  Woulffe  bottle  with  three  necks  and 
with  delivery  tubes  and  stopper  ground  in  the  necks  (Fig.  62,  a); 

Fig.  62 


KOH      Ba((JlI)-,,    CaClq        Aninml        CaCk    CaCk 
cage 


Apparatus  for  the  estimatif)n  of  COj  and  H2O  in  exhaled  air. 


three  .'j-incli  calcium  chloride  tubes,  with  side  tubes  and  perforated 
gla.ss  .stoppers,  opening  and  closing  the  flow  of  gas  (Fig.  62,  c,  e,  /); 


118  SPECIAL  PHYSIOLOGY 

Geissler's  potash  bulbs,  with  CaCl2  tube  ground  on  (g) ;  two  small 
flasks  (b,  h)  with  rubber  stoppers,  double  bored,  with  delivery  tubes 
fitted  as  shown  in  figure;  a  1 -litre  or  2-litre  bottle  with  very  wide 
mouth  to  use  as  animal  cage,  fitted  with  delivery  tubes  and  with  a 
cork  impregnated  with  paraffin;  siphon  apparatus,  as  figured,  consist- 
ing of  two  8-litre  bottles  with  paraffined  corks  and  tubes;  analytical 
balances;  laboratory  balances  (correct  to  0.01  grm.);  drying  oven; 
chemicals,  KOH,  Ba(OH)2,  CaCl2;  any  small  animal  whose  weight 
in  grams  does  not  exceed  one-fifth  the  volume  of  the  animal  cage 
expressed  in  cubic  centimetres. 

2.  Preparation.  (1)  Fill  the  calcium  chloride  tubes;  put  them 
into  the  drying  oven,  where  they  are  to  be  kept  at  a  temperature  of 
100°  to  120°  C.  for  several  hours;  cool  in  a  desiccator  and  weigh  upon 
the  analytical  balances  the  tubes  e  and  /,  recording  the  weight  in 
milligrams. 

(2)  Fill  the  Woulffe  bottle  and  the  Geissler's  bulbs  with  a  strong 
solution  (50  per  cent,  or  more)  of  KOH.  Fix  into  position,  upon  the 
Geissler  bulb,  its  filled  and  desiccated  CaClj  attachment,  and  fit 
to  each  end  a  rubber  connecting  tube;  clamp  with  strong  serre-fine 
forceps  and  weigh  upon  the  analytical  balances. 

(3)  Fill  the  flasks  b  and  h  with  a  strong  solution  of  Ba(OH)2. 
These  flasks  serve  simply  to  show  whether  or  not  the  COg  gas  has 
all  been  absorbed  by  the  KOH  through  which  it  has  just  passed. 

(4)  Pieces  e,  f,  and  g  should  be  fixed  to  a  light  wooden  rack,  by 
which  they  may  be  moved;  if  this  is  not  convenient  clamp  them  to 
supports. 

(5)  Join  up  the  apparatus  a,  b,  and  c. 

(6)  Fill  siphon  apparatus. 

(7)  Weigh  the  animal  cage  without  the  animal. 

3.  Operation.  (1)  Put  the  animal  into  the  cage;  fasten  the 
stopper  in  so  that  it  will  not  leak  air. 

(2)  Join  the  animal  cage  with  c  and  with  siphon  apparatus  at  i, 
leaving  out  for  this  preliminary  operation  the  apparatus  e,  f,  g,  and  h. 
Start  the  siphon  and  note  the  rate  of  flow  per  minute.  The  level 
of  the  water  in  the  lower  bottle  should  be  probably  1  metre  below 
that  in  the  upper  bottle.  Notice  whether  the  animal  seems  to  be 
respiring  normally.  If  so,  it  may  be  taken  for  granted,  after  ten 
minutes,  that  the  ventilation  is  sufficient.  If  it  seems  insufficient, 
one  has  only  to  increase  the  difference  of  level  in  the  two  siphon 
bottles. 

(3)  Disjoin  the  animal  cage  and  weigh  the  cage  with  the  contained 
animal  upon  the  laboratory  balances.  Note  the  time;  join  the  animal 
cage  in  circuit  again,  attaching  it  to  e,  and  attaching  h  to  the  siphon 
apparatus  at  i.  Start  the  siphon.  The  greater  resistance  to  be 
overcome  will  necessitate  a  greater  difference  in  the  level  of  the 
two  bottles  in  order  to  ventilate  at  the  same  rate  as  before.     To 


RESPIRATION  ]19 

test  joints  place  the  finger  over  the  distal  tube  of  the  Woulffe  bottle 
(a);  if  the  joints  are  all  right  the  siphon  stream  will  stop  after  a 
few  moments.  When  the  water  in  the  upper  bottle  is  lowered  nearly 
to  the  end  of  the  siphon,  clamp  the  tube  joining  h  to  i,  set  the  empty 
bottle  upon  the  floor  and  the  full  bottle  on  the  higher  level,  join  the 
tube  at  k,  and  unclamp.  This  whole  change  need  only  occupy  a 
few  seconds.  If  it  is  desired  to  make  a  determination  of  the  amount 
of  oxygen  which  the  animal  consumes  in  a  given  time,  the  air  that 
passes  out  of  the  ventilating  apparatus  after  the  second  change  may 
be  caught  and  tested. 

(4)  It  is  evident  that  in  the  afferent  apparatus  (a,  h,  and  c)  one 
has  a  means  of  robbing  the  air  of  COj  and  H2O,  thus  furnishing  the 
animal  with  pure  dry  air.  It  is  further  evident  that  in  the  afferent 
apparatus  one  has  a  means  of  collecting  absolutely  all  of  the  COj 
and  H2O  given  off  from  the  animal  during  the  experiment.  Further, 
the  weights  before  and  after  will  show  just  how  much  of  these  excreta 
have  been  passed  into  the  collecting  apparatus. 

(5)  Note  the  time  (one  hour  or  more);  damp  siphon  tube;  turn 
the  stoppers  off  e  and  /,  clamp  x  and  y;  disjoin  d  and  weigh  it. 

(6)  Weigh  e,  weigh  /,  weigh  g. 

4.  Observations.  (1)  How  much  has  the  animal  lost  in  weight 
during  the  period  of  observation? 

(2)  How  much  water  left  the  animal  cage  during  the  period  of 
observation  ? 

(3)  What  was  the  source  of  this  water? 

(4)  Did  the  animal  micturate  or  defecate  during  the  time  of  the 
experiment?  If  so,  is  this  to  be  looked  upon  as  a  source  of  error  in 
the  experiment?  Would  such  an  occurrence  tend  to  increase  or 
decrease  the  amount  of  water  caught  in  the  CaClj  tubes  e  and  jf 
Would  it  interfere  in  any  way  with  the  experiment?  If  so,  how 
may  such  a  source  of  error  be  avoided  or  corrected? 

(5)  How  much  COj  left  the  animal  cage  during  observation? 

(6)  What  is  the  total  amount  of  COj  and  HjO  collected? 

(7)  Does  the  amount  of  these  excreta  collected  equal  the  loss  in 
weight  of  the  animal  ?  What  should  the  relation  of  these  two  quanti- 
ties be?     Explain  in  full. 

(8)  What  is  the  respiratory  quotient? 

(9)  Formulate  several  problems  which  may  be  solved  with  this 
method. 

VII.     TO   DETERMINE   THE   AMOUNT    OF    OXYGEN    CONSUMED 
BY   AN   ANIMAL   IN   A   GIVEN   TIME. 

1.  Preparation.  The  oxygen  is  determined  by  a  volumetric 
method,  using  two  or  more  gas  burettes  and  a  solution  of  potassium 
pyrogallate. 


120 


SPEC  I  A  L  PH  YSIOL  OGY 


The  solution  of  potassium  pyrogallate  is  prepared  by  mixing  two 
parts  of  25  per  cent,  aqueous  solution  of  KOH  and  one  part  of  5  per 
cent,  aqueous  solution  of  pyrogallic  acid. 

Comparison  must  be  made  between  the  oxygen  content  of  the 
expired  air  and  that  of  the  atmosphere  at  the  time  of  the  experiment. 
If  it  is  desired  to  calculate  the  respiratory  quotient  it  will  be  necessary 
to  make  the  oxygen  analysis  from  the  air  that  traversed  the  animal 
cage  in  the  previous  experiment  when  the  CO2  was  being  determined. 

If  it  is  not  desired  to  compute  the  respiratory  quotient  it  will  be 
necessary  only  to  have  it  traverse  the  animal  cage,  drawn  through 
by  the  ventilating  apparatus. 

The  air  should  come  into  the  cage  from  out  of  doors  (brought  in 
through  glass  or  rubber  tubes  from  the  window). 


Fig.  63 


% 


n 


Position  1. 


Position  2. 
Gas  burettes  to  determine  oxygen. 


Position  3 


2.  Operation.  These  two  constituents  of  the  pyrogallate  should 
be  mixed  in  the  pressure  tube  of  the  gas  apparatus  just  before  the 
analysis  is  made.  To  collect  samples  of  air  for  analysis,  one  fills 
the  gas  burette  (Fig.  63,  A)  with  water  by  suction.  Connection  is 
then  made  between  the  exit  tube  at  k,  of  the  respiration  apparatus 
used  in  the  previous  experiment  (see  Fig.  62),  and  the  upper  end  of 
the  gas  burette  as  shown  in  Fig.  63,  position  1 ;  the  respired  air  flows 
in,  displacing  the  water.  The  stopcocks  are  now  turned  so  that  no 
air  can  escape  from  the  burette.  The  rubber  tube  of  the  pressure 
tube  B,  which  has  been  filled  with  the  potassium  pyrogallate,  is  now 


RESPIBA  TION  121 

connected  to  the  lower  end  of  the  gas  burette.  After  all  the  air  has 
been  expelled  from  the  connections,  turn  the  three-way  stopcock  in 
such  a  position  as  to  permit  the  pyrogallate  to  flow  up  into  the  gas 
burette,  coming  in  contact  with  the  air  to  be  analyzed.  The  pressure 
tube  should  now  be  elevated  as  high  as  the  connecting  rubber  will 
permit  and  the  potassium  pyrogallate  solution  allowed  to  run  into 
the  burette  A.  The  clamp  on  the  connecting  tube  should  now  be 
applied  to  it  close  to  the  lower  end  of  the  burette. 

This  operation  made  positive  pressure  in  the  burette,  thereby 
causing  a  more  rapid  absorption  of  the  oxygen.  The  burette  should 
now  be  taken  by  the  experimenter  and  its  ends  alternately  raised 
and  lowered.  At  frequent  intervals  he  should  loosen  the  clamp  on 
the  connecting  rubber  tube  and  raise  the  pressure  tube,  thus  permit- 
ting potassium  pyrogallate  solution  to  take  the  place  of  the  oxygen 
as  it  is  absorbed.  This  procedure  should  continue  ten  minutes,  after 
which  the  clamp  on  the  connecting  rubber  tube  should  be  loosened. 
The  burette  and  its  pressure  tube  should  be  allowed  to  remain  ten 
minutes  longer,  at  the  end  of  which  time  the  solution  in  the  burette 
should  be  brought  to  a  level  with  the  solution  in  the  pressure  tube 
by  elevating  or  lowering  the  tube.  This  causes  the  air  in  the  burette 
to  be  under  the  atmospheric  pressure  existing  at  that  time.  The 
reading  for  the  amount  of  oxygen  is  now  taken. 

To  calculate  the  amount  of  oxygen  consumed  by  the  animal,  one 
subtracts  the  amount  of  oxygen  found  in  the  respired  air  from  that 
found  in  the  normal  air.  At  least  one  sample  should  be  analyzed 
from  each  10  litres  of  respired  air,  the  average  being  used  to  obtain 
the  result. 

VIII.    THE   RESPIRATORY  QUOTIENT. 

The  respiratory  quotient  being  the  ratio  between  the  volume  of  car- 
bon dioxide  exhaled  and  that  of  oxygen  consumed  (R.Q.=  — r^ — ^^  ) , 

it  may  be'computed  from  data  given  in  Exercises  VI.  and  VII.,  or  it 
may  be  directly  determined  in  the  following  manner: 

1.  Appliances.  Ventilating  apparatus  (Fig.  64);  animal  cage; 
CaClj  tube;  Geissler  bull)s;  two  barium  hydrate  flasks;  25  percent, 
solution  of  KC)II;  5  per  cent,  solution  of  pyrogallic  acid;  two  gas 
burettes  with  pressure  tubes;  guinea-pig  or  small  rabbit. 

2.  Preparation.  Pass  one  end  of  the  glass  tube  out  through  hole 
in  wiiiflow  sash;  to  inner  end  attach  a  rubber  tube  to  whose  other 
end  is  joined  a  V><i(()\\)^  flask,  followed  by  cage,  diC\^  tube,  Geissler 
bulbs,  barium  flask,  and  ventilating  apparatus,  as  shown  in  the 
figure.     Weigh  animal  cage.     Note  temperature  of  room. 

3.  Operation.  Put  the  animal  into  the  cage;  take  weight.  Start 
the  ventilation,  noting  tlie  time.     While  the  first  pressure  bottle  is 


122 


SPECIAL  PHYSIOLOGY 


< 


RESPIRATION  123 

emptying  take  a  specimen  of  out-of-door  air  and  determine  its  oxygen, 
taking  care  to  let  it  reach  room  temperature  before  measuring  it. 

After  the  second  change  of  the  ventilating  apparatus  take  100  c.c. 
of  air  from  every  8  or  10  htres  of  air  that  traverse  the  cage  and 
determine  the  oxygen.  Note  very  carefully  the  amount  of  air  that 
traverses  the  animal  cage  and  keep  the  ventilating  stream  as  regular 
as  possible. 

At  the  end  of  the  experiment  take  a  second  100  c.c.  of  air  from 
out  of  doors  and  determine  its  oxygen. 

4.  Observations.  (1)  How  many  cubic  centimetres  of  oxygen 
has  the  animal  consumed  during  the  experiment,  measured  at  the 
room  temperature  and  the  pressure  read  from  the  barometer? 

(2)  Reduce  the  volume  of  oxygen,  as  determined  under  the  con- 
ditions given  above,  to  the  volume  which  it  would  represent  if  meas- 
ured under  standard  conditions  of  0°  C.  and  760  mm.  pressure. 

(3)  How  many  milligrams  of  COj  were  caught  by  the  Geissler  bulb? 

(4)  How  many  cubic  centimetres  of  COj  at  0°  C.  and  760  mm. 
barometric  pressure  would  be  equal  to  number  of  milligrams  deter- 
mined under  (3). 

(5)  What  is  the  respiratory  quotient?     R.  Q.=       " ^  — 


(6)  Is  the  subject  of  the  experiment  a  carnivorous,  omnivorous, 
or  herbivorous  animal? 

(1)  What  has  been  the  diet  of  the  animal  during  the  last  three 
days  before  the  experiment? 

(8)  How  long  before  the  experiment  had  the  animal  eaten? 

(9)  Determine  the  influence  of  diet  on  respiratory  quotient. 

(10)  Determine  the  influence  of  fasting  on  respiratory  quotient. 


IX.    RESPIRATION  UNDER  ABNORMAL  CONDITIONS. 

1.  Appliances.  Six  small  animals — c-g-,  rats  or  guinea-pigs;  six 
wide-mouthed  bottles  or  jars,  which  may  be  sealed;  scales  or  large 
balances;  COj  generator;  water-bath;  operating  case;  dissecting 
boards. 

2.  Preparation.  Determine  the  weight  of  animals  "a,"  "b,"and 
"c."  Choose  a  receptacle  whose  cubic  contents  is  not  over  twice 
as  many  cubic  centimetres  as  the  weight  of  animal  "a"  in  grams. 
Choose  .second  and  third  receptacles  whose  contents  represent  about 
10  c.c.  to  ]  gnn.  of  animals  "b"  and  "c,"  respectively. 

'.'>.  Operation.  I.  Prehminary.  (a)  Put  animal  "a"  into  the  small 
jar  "a;"  count  resj)i rations;  close  the  jar. 

(h)  Put  animal  "b"  into  jar"  b."  Before  closingcount  respirations; 
close  air-tight. 

{(■)   Fill  jar  "c"  one-third  full  oi  water  and  displace  the  water  with 


124  SPECIAL  PH YSIOL OGY 

COj.     Put  animal  "c"  into  the  jar,  taking  care  to  allow  as  little 
loss  of  CO3  as  possible;  close;  count  respirations. 

(d)  Fill  jar  "d"  full  of  water  and  displace  with  CO2.  Put  animal 
"d"  into  jar,  taking  care  to  allow  as  little  loss  of  COg  as  possible; 
close  jar  and  count  respirations. 

(e)  Put  an  animal  into  a  jar;  cover  the  mouth  of  the  jar  with  a 
towel;  insert  into  the  jar  the  end  of  a  rubber  tube  through  which 
illuminating  gas  (a  mixture  of  CO  with  various  other  gases)  may 
be  let  into  the  jar.  Let  the  gas  in  in  little  momentary  puffs  every 
five  minutes,  noting  the  effect  upon  the  animal. 

II.  Post-mortem  Examination.  After  an  animal  dies  fix  it  to  the 
dissecting  board  and  open  the  abdominal  and  thoracic  cavities;  take 
great  care  not  to  cut  a  large  bloodvessel;  pin  the  flaps  out  so  that 
all  of  the  organs  will  be  exposed  in  place. 

4.  Observations,  (a)  Respiration  in  Small  Closed  Space.  (1)  Make 
a  careful  record  of  number  of  respirations  and  general  condition  of 
animal  "a"  in  the  normal  state,  and  at  the  end  of  every  five  minutes 
after  the  closure  of  the  jar. 

^Miat  changes  in  rate  or  depth  of  respiration  have  been  noted? 

(2)  Note  all  abnormal  signs  and  symptoms. 

(3)  On  post-mortem  examination  record  the  condition  of  heart, 
large  bloodvessels,  lungs,  liver,  kidneys,  and  the  general  appearance 
of  the  tissues. 

(4)  Compare  the  conditions  with  those  found  in  a  normal  animal, 
prepared  by  the  demonstrator. 

(b)  Respiration  in  a  Larger  Closed  Space.  (5)  Note  all  symptoms  of 
animal  "b"  every  five  minutes  after  confinement  in  the  jar. 

(6)  Make  a  post-mortem  examination;  record  in  detail  the  con- 
dition of  the  organs  as  in  the  case  of  animal  "a." 

(7)  Compare  animal  "b"  with  normal  animal. 

(8)  Compare  animal  "b"  with  animal  "a." 

(c)  Respiration  in  an  Atmosphere  of  One-third  COg.  (9)  Note  all 
symptoms  at  intervals  of  five  minutes. 

(10)  Compare  these  observations  with  corresponding  ones  from 
animal  "a"  and  "b."    What  are  your  conclusions? 

(11)  Make  a  post-mortem  examination;  make  a  record  as  before. 

(12)  Compare  appearances  in  animal  "e"  with  those  in  the 
normal  animal;  with  those  of  animal  "a";  with  those  of  animal  "b." 

(13)  iNIake  a  generalized  statement  of  the  facts  discovered  in  the 
experiments. 

(14)  What  is  the  cause  of  death  when  an  animal  is  enclosed  in  a 
small  space? 

(15)  What  is  the  cause  of  death  when  an  animal  is  enclosed  in  a 
large  space? 

(16)  Have  the  relations  which  you  have  discovered  any  bearing 
upon  the  future  development  of  animal  life  upon  the  earth? 


RES  PIE  A  TIOX  125 

{d)  Respiration  in  COj  ("Choke-damp").  (17)  Lower  a  lio-hted 
candle  into  a  jar  of  CO,.     Record  results. 

(18)  What  happened  to  the  animal  when  it  was  lowered  into  an 
atmosphere  of  COj? 

(19)  Record  post-mortem  appearances. 

(e)  Respiration  in  an  Atmosphere  of  One -third  Illuminating  Gas 
(00 -f).     Record  all  symptoms. 

Record  post-mortem  appearances. 

How  does  death  in  an  atmosphere  of  CO  compare,  as  to  symptoms, 
with  death  in  an  atmosphere  of  COj. 

Compare  it  in  turn  with  other  forms  of  death  as  induced  in  this 
and  the  previous  chapter. 

Compare  the  post-mortem  appearances  in  this  case  with  those  in 
preceding  cases. 


X.   TO  DETERMINE  THE  INFLUENCE  OF  THE  PHRENIC  NERVE. 
THE  NORMAL  PHRENOGRAM. 

1.  Appliances.  Operating  case;  chppers;  rabbit  board  or  dog 
board;  rabbit  or  dog;  ether  or  chloroform ;  anaesthesia  cone;  tambours, 
arranged  as  used  to  record  the  rabbit  stethogram ;  beaker  with  warm 
water;  inductorium;  one  dry  cell;  two  keys;  vagus  electrode;  seven 
wires;  a  piece  of  glass  rod  10  cm.  which  has  been  rounded  at  one 
end  and  sharpened  at  the  other. 

2.  Preparation.  Fix  the  animal  to  the  board;  anaesthetize;  clip 
the  anterior  median  region  of  abdomen.  Set  up  electric  apparatus 
with  short-circuiting  key  in  secondary  coil  and  with  Xeef  hammer 
in  primary  circuit. 

3.  Operation.  F'rom  the  posterior  extremity  of  the  xiphoid 
appendix  make  a  median  incision  through  the  abdominal  walls. 
The  incision  should  be  just  large  enough  to  admit  the  glass  rod,  and 
should  be  located  in  the  rabbit  1  cm.  from  the  tip  of  the  xiphoid 
and  in  the  dog  3  cm.  from  the  xiphoid. 

Clamp  with  the  serre-fines  any  small  vessels  which  may  be 
oozing. 

The  rounded  end  of  the  glass  rod  is  passed  through  the  abdom- 
inal wall  and  held  against  the  diaphragm  A.  The  point  is 
inserted  into  the  cork  button  of  the  receiving  tambour.  (See 
Fig.  65.)  Any  contraction  of  the  diaphragm  presses  the  round  end 
V>ackward  and  the  rod  is  forced  posteriorly,  slipping  back  and  forth 
through  the  liole  in  the  body  wall,  the  point  is  pressed  back,  and  the 
lever  of  the  recording  tambour  rises.    Trace  a  phrenogram. 

In  the  mean  time  let  another  member  of  the  division  dissect  out 
the  left  phrenic  nerve. 

This  operation  to  expose  the  phrenic  nerve  is  the  most  difficult 


126 


SPECIAL  PHYSIOLOGY 


operation  yet  attempted  in  any  of  these  exercises.  The  nerve  is  very 
small  and  lies  deeply  buried  in  the  neck  not  far  from  the  spinal 
column  and  in  close  relation  to  other  nerves,  making  it  difficult  so 
to  describe  its  relations  that  the  operator  will  be  certain  when  he  has 
found  it.  The  only  sure  course  is  to  test  it  by  stimulation,  and  if 
it  causes  a  contraction  of  the  corresponding  side  of  the  diaphragm 
the  operator  may  be  certain  he  has  found  either  the  main  trunk  or 
one  of  its  three  roots. 

The  cutaneous  incision  should  be  on  the  course  of  the  sterno- 
mastoid  muscle,  just  dorsal  to  the  course  of  the  external  jugular  vein. 
The  cutaneous  incision  should  be  ample,  extending  to  the  clavicle 
at  least  5  cm.  long  anteriorly  in  the  rabbit  and  correspondingly  long 
if  the  dog  is  used. 


Fig.  65 


Phrenograph  for  taking  tracings  of  ttie  movements  of  the  diaphragm :  T,  tambour  joined 
to  recording  tambour  and  fitted  with  a  cork  button  (C);  a  glass  rod  passes  through  a  slit  in  the 
abdominal  wall  at  i^'and  rests  against  the  diaphragm  at  A. 


Dissect  through  the  subcutaneous  tissues  and  separate  the  skin 
flaps  widely,  pressing  the  external  jugular  toward  the  median  line. 
The  superficial  layer  of  muscles  consists  of  the  sternomastoid  on 
the  median  side  and  the  cleidomastoid  laterally  in  the  rabbit  (the 
cephalohumeral  in  the  dog). 

Divide  the  connective  tissue  that  separates  these  two  muscles  and 
pass  to  the  deeper  layer.  On  the  median  side  one  sees  the  carotid, 
the  internal  jugular,  and  the  nerves  that  lie  in  close  relation  to  them; 
drawing  the  cleidomastoid  outward  one  exposes  the  roots  of  the 
brachial  plexus,  emerging  from  between  the  deep  muscles  of  the 
neck  and  passing  downward  and  backward  toward  the  axilla. 

Very  careful  dissection  of  the  delicate  connective  tissue  which  lies 
over  the  roots  of  the  brachial  plexus  will  reveal  a  fine  nerve  thread 
crossing  these  roots  very  near  to  the  line  where  they  first  come  into 
view,  and  passing  posteriorly  it  gradually  draws  nearer  to  the  median 
line  as  it  passes  under  the  clavicle  (under  the  subclavian  artery  in 
the  dog).  This  nerve  is  the  phrenic.  Carefully  dissect  it  out  as  near 
the  clavicle  as  possible,  lift  it  gently  on  the  nerve  hook,  and  place  it 


RESPIRATION  127 

in  the  groove  of  a  shielded  electrode.  Stimulate  gently.  If  you  have 
dissected  out  only  the  phrenic  and  posterior  to  its  three  tributaries, 
the  stimulation  will  be  followed  by  a  tetanic  contraction  of  the 
corresponding  side  of  the  diaphragm.  If,  however,  one  has  taken 
up  with  the  phrenic  a  communicating  thread,  passing  from  one  root 
of  the  brachial  plexus  to  another,  the  stimulation  will  be  followed 
by  a  tetanic  contraction,  not  only  of  the  diaphragm,  but  also  of  some 
of  the  muscles  of  the  front  leg  of  the  side  operated  upon.  As  this 
will  disturb  the  result  the  error  must  be  corrected.  The  nearer  the 
clavicle  one  can  get  the  nerve  the  more  unlikely  he  is  to  get  nerve 
fibres  belonging  to  the  brachial  plexus. 

4.  Observations,  (a)  Tactile  Observation  of  the  Diaphragm.  (1)  In 
what  condition  is  the  diaphragm  during  inspiration?    Expiration? 

(2)  In  what  position  is  the  diaphragm  during  these  two  phases 
of  respiration? 

(3)  What  parts  of  the  diaphragm  make  the  greatest  change  of 
position  during  inspiration? 

(4)  What  causes  the  diaphragm  to  arch  anteriorly  during  normal 
expiration?  Are  the  conditions  changed  during  the  present  observa- 
tions ? 

(5)  Are  the  diaphragmatic  movements  synchronous  with  the  costal 
movements  ? 

(h)  The  Normal  Phrenogram.  (6)  Take  a  phrenogram.  What  may 
be  learned  from  it? 

(I)  Without  varying  the  adjustment  of  the  phrenograph  take 
a  tracing  while  repeatedly  interrupting  the  respiration  by  hold- 
ing the  nostrils.  What  does  the  phrenogram  show?  What  is  the 
interpretation  ? 

What  effect  upon  intrathoracic  pressure  would  holding  the  nostrils 
have  ? 

(c)  The  Phrenic  Nerve  and  its  Function.  (8)  Describe  minutely  the 
relations  of  the  nervus  phrenicus  in  the  neck. 

(9)  Cut  the  nerve  while  tracing  a  phrenogram  from  the  left  side 
of  the  diaphragm.     Note  the  result. 

(10)  Take  a  phrenogram  from  the  right  side  of  the  diaphragm. 
Does  it  differ  essentially  from  the  normal? 

(II)  While  taking  the  left  phrenogram  stimulate  the  distal  end  of 
the  left  phrenic  nerve.     Interpret  the  result. 

(12j  While  taking  a  right  phrenogram  stimulate  the  distal  end  of 
the  left  phrenic  nerve.     Interpret  the  result. 

(13j  Dissect  out  and  cut  the  right  phrenic  nerve.  Does  the 
diaphragm  cease  to  move?  If  it  moves,  is  its  movement  active  or 
passive?  Does  it  move  backward  (hiring  inspiration  anfl  forward 
during  expiration?  If  so,  what  causes  it  to  make  these  movements? 
If  the  movements  are  reversed,  what  has  caused  the  change? 

Account  for  the  phenomena.     Kill  the  animal  with  chloroform. 


CHAPTER   V. 

NORMAL  HEMATOLOGY. 

INTRODUCTION. 

The  examination  of  the  blood,  like  that  of  the  urine,  gives  a  posi- 
tive diagnosis  in  a  number  of  diseases.  It  assists  the  diagnosis  in 
many  diseases  and  is  often  of  much  value  negatively.  It  is  important, 
then,  to  be  familiar  with  the  characteristics  of  normal  blood.  The 
examination  of  the  normal  blood  consists  of  an  actual  study  of  the 
blood  by  use  of  the  microscope  and  the  determination  of  many  of 
its  properties  by  the  use  of  various  instruments,  which  will  be 
described  in  the  text.  The  accurate  use  of  the  instruments  can  be 
learned  only  by  experience.  While  the  instruments  are  delicate  and 
easily  broken,  yet  the  technique  of  their  use  is  easily  mastered  by 
the  student  if  he  is  careful,  accurate,  and  persevering.  The  technique 
once  acquired  can  be  quickly  regained  in  later  years,  although  it 
may  apparently  be  forgotten  for  the  time  being.  Speed  in  the  tests 
can  be  obtained  only  by  continuous  practice.  Theoretically  all  these 
instruments  are  accurate,  but  because  of  the  minute  quantity  of 
blood  used,  slight  inaccuracies  will  be  multiplied  in  the  final  results 
and  may  be  large  or  small  according  to  the  experience  and  careful- 
ness of  the  observer.  By  knowing  where  these  errors  are  possible 
and  avoiding  them  by  the  best-known  methods,  and  by  adopting  a 
definite  method  of  use  of  each  instrument,  these  inaccuracies  can 
be  largely  eliminated  and  good  comparative  results  obtained.  In 
the  use  of  blood  instruments  the  observer  must  constantly  avoid 
manufacturing  results.  There  is  always  the  tendency  to  read  into 
the  test  a  preconceived  result.  This  is  best  governed  by  control 
tests  and  by  repeated  tests.  When  one  can  repeat  a  test  three  or 
four  times  with  the  same  individual's  blood  and  obtain  approximately 
the  same  results  he  is  quite  proficient. 

Reference  Books. — Clinical  Examination  of  the  Blood,  by  Cabot.  Clinical  Pathology  of 
the  Blood,  by  Ewing.  Clinical  Haematology,  by  Da  Costa.  Histology  of  the  Blood,  by  Ehrlich 
and  Lazarus.      Text-book  on  Physiology,  by  Hall.      Works  on  Histology  and  Physiology. 

GENERAL  DIRECTIONS. 

All  blood  instruments  must  be  perfectly  clean  and  dry  if  the  best 
results  are  to  be  obtained.  The  various  pipettes  are  cleaned  by  the 
use  of  hydrogen  peroxide  and  distilled  water;  they  are  then  dried 


NORMAL  H^MA TOL OGY  129 

by  the  use  of  alcohol  to  remove  the  water,  followed  by  ether,  which 
will  evaporate  quickly  aud  remove  the  alcohol. 

Hydrogen  peroxide  oxidizes  organic  matter;  alcohol  and  ether 
coagulates. 

The  cleaning  fluids  (hydrogen  peroxide  and  water)  are  used  by 
filling  the  pipette  and  rolling  it  for  a  few  minutes  between  the  thumb 
and  fingers  and  then  blowing  or  drawing  the  fluid  out. 

In  the  use  of  the  drying  fluids  (alcohol  and  ether)  do  not  blow 
the  fluids  out  of  the  pipettes,  as  the  moisture  of  the  breath  will  defeat 
the  object  which  one  is  seeking.  Having  filled  the  pipette  with 
alcohol  or  ether,  draw  it  into  the  rubber  tube,  remove  the  rubber 
tube  from  the  pipette,  blow  the  fluid  out  of  the  rubber  tube,  replace 
it  upon  the  pipette,  then  draw  air  through  the  pipette.  After  using 
alcohol  in  this  way,  followed  by  ether,  one  may  be  assured  that  the 
pipette  is  absolutely  dry. 

For  the  student's  work,  secure  the  blood  from  the  lobe  of  the 
ear  or  the  side  of  the  tip  of  the  third  finger.  The  ear  is  better,  as 
it  contains  fewer  nerves,  gives  more  blood,  and  will  continue  to  bleed 
for  a  longer  time.  The  ear  or  finger  should  be  lightly  washed  with 
a  towel  moistened  with  distilled  water,  then  dried  with  the  towel  to 
remove  any  dirt  or  loose  epithelial  cells.  The  needle  used  should 
be  a  fair-sized  glover's  needle.  It  is  a  three-sided  needle,  the  sides 
of  which  are  so  ground  that  each  has  a  fine  saw-edge  and  will  cut 
and  not  crush  the  tissues  as  a  saddler's  needle  will.  The  needle 
should  be  kept  clean  with  distilled  water  and  hydrogen  peroxide,  and 
sterilized  with  alcohol. 

The  puncture  should  be  made  by  holding  the  lobe  of  the  ear 
between  the  thumb  and  finger  and  pricking  lengthwise  of  the  ear 
in  its  lowest  part.  The  needle  should  enter  about  one-quarter  of 
an  inch,  and  should  be  thrust  in  quickly  while  the  thumb  and  finger 
hold  the  ear,  and  when  withdrawn  it  should  be  given  a  half-turn 
and  be  quickly  removed.  The  first  drop  of  blood  should  always  be 
wiped  away  to  moisten  the  skin  with  blood,  and  also  because  it  clots 
quicker  than  the  following  drops. 

The  blood  should  gradually  ooze  out  of  itself.  It  should  never 
be  forcibly  squeezed  out  by  pinching,  as  that  will  give  an  abnormal 
specimen;  but  the  ear  may  he  gently  pressed  an  inch  or  so  above 
the  puncture,  to  make  the  blood  flow  more  freely. 

To  fill  a  pipette  by  suction,  take  the  lobe  of  the  ear  between  the 
thumb  and  finger  of  the  left  hand,  standing  l)ehind  and  to  the  right 
when  using  the  right  ear  and  in  front  and  to  the  left  when  using 
the  left  ear.  Place  the  tip  of  the  pipette  upon  the  thumb  that  is 
behind  the  ear  hold  the  pipette  with  the  right  hand  near  its  upper 
extremity,  with  the  marks  showing  in  front;  then,  by  turning  the 
thumb,  insert  the  capillary  point  into  the  drop  of  blood  and  do  not 
allow  it  to  touch  the  skin  of  the  ear;  the  column  of  blood  drawn  into 

9 


130 


SPECIAL  PHYSIOLOGY 


the  capillary  must  be  accurate  and  complete.  It  must  not  remain 
short  of  or  go  beyond  the  mark  desired,  and  air  must  not  be  allowed 
to  enter  the  pipette.  If  any  of  these  errors  take  place  the  pipette 
must  be  recleaned,  dried,  and  filled  again. 

When  properly  filled,  any  blood  adhering  to  its  outer  surface 
must  be  completely  removed  before  proceeding  farther.  It  is  better 
to  have  a  large  drop  of  blood  at  first  than  to  use  two  or  three  small 

drops,  as  there  is  less  liability  of  getting 
air  into  the  capillary  and  of  the  blood 
clotting. 


Fig.  66 


I.  THE  COUNTING  OF  THE  BLOOD 
CORPUSCLES. 


Introductory.  In  health  the  number 
of  red  cells  in  the  blood  is  quite  constant. 
The  variations  that  occur  are  quite  small 
and  are  due  to  normal  processes.  In  the 
male  there  are  about  5,000,000  red  cells 
in  each  cubic  millimetre.  In  the  female 
there  are  about  4,500,000  red  cells.  Any 
deviation  from  normal  health  quickly 
causes  a  diminution  in  the  number  of 
red  cells.  In  fact,  simple  unhygienic 
surroundings  or  habits  are  sufiicient  to 
speedily  reduce  the  number  of  red  cells 
without  other  demonstrable  pathological 
conditions. 

The  life  of  the  red  cell  is  probably  of 
about  two  weeks'  duration.  There  are 
approximately  in  the  normal  male's  blood 
200,000,000,000  red  cells.  Then  accord- 
ing to  the  length  of  the  lifetime  of  the 
cells  about  14,000,000,000  red  cells  die 
and  must  be  disposed  of  each  day.  A  cor- 
responding number  must  be  manufactured 
each  day  in  order  to  keep  the  number 
It  will  be  readily  seen  that  such  an  im- 
mense process,  which  depends  upon  perfect  elimination  as  well  as 
assimilation,  can  be  disturbed  very  easily.  It  is  important  that  this 
fact  about  the  blood  be  thoroughly  understood.  Even  though  the 
physician  may  not  estimate  the  number  of  red  cells  in  every  case, 
yet  he  must  recognize  the  fact  that  every  disturbing  element  in  the 
normal  body  must  disturb  the  number  of  red  cells  contained  therein. 
There  are,  then,  two  objects  to  be  gained  by  actually  counting  the 


The  Thoma-Zeiss  blood-counter. 
The  pipette  for  use  in  counting  the 
red  corpuscles. 

within  its  normal  limits. 


NORMAL  HEMATOLOGY 


131 


red  cells  and  estimating  their  number.  First,  to  gain  a  clear  idea 
and  understanding  of  the  number  of  red  cells  in  normal  blood,  and, 
second,  to  be  able  readily  and  accurately  to  estimate  the  number  of 
red  cells  per  cubic  millimetre  in  any  given  clinical  case. 


Fig.  67 


The  haematocrit.  The  attachment  at  the  ur)per  end  of  the  vertical  shaft  is  made  to  rotate  at 
a  speed  of  7000  to  10,000  per  minute  by  means  of  the  eear-work  of  the  body  of  the  instrument. 
Each  arm  of  the  rotating  attachment  is  provided  with  a  capillary  tube  which  is  graduated  into 
100  divisions.  If  the  tube  be  filled  with  blood  and  rotated  for  two  or  three  minutes  at  the 
speed  abfn-e  mentioned  the  corpuscles  will  be  thrown  to  the  outer  end  and  the  volume  per  cent, 
may  be  read  off  on  the  tube.      B,  an  enlarged  view  of  tube  with  centrifugalized  blood. 

There  are  three  methods  of  estimating  the  number  of  red  cells 
per  cubic  millimetre. 

1.  The  Thoma  Haemacytometer.  An  instrument  by  which,  with 
accurate  dilutifHi,  the  corpuscles  may  be  actually  seen  and  counted 
in  a  known  space  (Fig.  66). 


132  SPECIAL  PHYSIOLOGY 

2.  The  Oliver  Haemacytometer.  This  instrument  depends  upon  the 
transmission  of  a  transverse  hne  of  hght  from  a  candle  through  a 
flat  glass  tube.  The  blood  stops  this  light  until  a  certain  dilution 
is  obtained.  The  tube  is  graduated  to  read  in  the  number  of  cells 
per  cubic  millimetre  of  the  blood  used  according  to  the  dilution. 

3.  The  Haematocrit.  By  this  instrument  is  obtained  the  volume 
of  the  corpuscular  elements  in  the  blood  by  centrifugation.  From 
this  the  number  of  red  cells  per  cubic  millimetre  may  be  estimated 
except  in  some  special  cases  (Fig.  67). 

A.  To  Count  the  Red  Blood  Corpuscles. 

Appliances.  Microscope  with  one-fifth-inch  objective  and  me- 
chanical stage;  Thoma  corpuscle  counter,  consisting  of  the  ruled 
counting  slide  and  the  diluting  pipettes;  glover's  needle;  three  small 
beakers  and  as  many  open  dishes. 

Preparation.  Wash  the  counting  slide  with  water  or  soap  and 
water  only  when  it  needs  it;  the  less  it  is  handled  the  better.  Usually 
rinsing  it  in  clean  water  and  drying  with  a  cloth  is  sufiicient.  Prepare 
small  beakers  of  distilled  water  and  the  diluting  solution.  Clean  the 
pipette  as  usual. 

Technique.  Having  prepared  the  apparatus  and  solutions,  make 
the  puncture  and  fill  the  pipette  by  gently  sucking  a  continuous 
column  of  blood  up  to  the  mark  "0.5"  or  "1"  on  the  pipette,  which 
is  near  the  bulb.  Wipe  the  end  of  the  pipette  free  from  blood  with 
a  clean  cloth,  but  do  not  allow  any  blood  to  be  drawn  out  by  the 
capillary  attraction  of  the  cloth.  As  soon  as  possible  now  insert  the 
point  of  the  pipette  into  the  diluting  solution  and  suck  up  a  con- 
tinuous stream  of  solution  until  the  mark  "101"  above  the  bulb  is 
reached.  Roll  the  bulb  between  the  thumb  and  finger  as  the  blood 
enters  the  bulb. 

If  there  is  not  blood  enough  to  reach  the  mark  "1,"  draw  it  only 
to  mark  "0.5"  and  proceed  in  the  same  manner.  Now  hold  the 
pipette  in  the  horizontal  position  with  ends  free  and  roll  it  back 
and  forth  for  three  minutes  to  thoroughly  mix  the  blood  and  solu- 
tion. When  thoroughly  mixed  blow  out  the  contents  of  the  cap- 
illary below  the  bulb  and  then  place  a  small  drop  on  the  marked 
plate  of  the  counting  slide,  putting  just  enough  of  the  mixture  on 
it  to  fill  the  space  between  the  marked  plate  and  cover-glass,  and 
being  careful  not  to  allow  any  of  the  mixture  to  get  into  the  moat. 
Adjust  the  cover-glass  over  the  drop  quickly  and  carefully  by  placing 
one  edge  of  cover-glass  in  contact  with  the  slide  and  letting  the 
opposite  edge  down  gently  with  a  needle. 

Place  the  counting  slide  when  properly  filled  under  the  microscope 
and  find  the  upper  left-hand  corner  of  the  marked  area.  Wait  until 
the  corpuscles  come  to  rest  upon  the  surface  of  the  marked  plate, 


NORMAL  HEMATOLOGY 


133 


then  begin  the  actual  estimation  by  counting  all  the  corpuscles  in 
the  first  marked  space,  including  those  that  are  on  the  upper  and 
left-hand  lines  of  the  space.  Then  count  those  in  the  space  to  the 
right,  including  the  corpuscles  on  the  upper  and  left-hand  lines  as 
before.  Continue  counting  each  space  to  the  right  until  six  spaces 
are  counted;  then  drop  down  to  the  next  space  below  and  count 


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Appearance  of  slide  under  about  500  diameters  magnification.     One  counts  all  corpuscles 
which  lie  upon  the  upper  and  left  boundaries  of  each  square. 

each  space  to  the  left  until  six  spaces  in  the  second  row  are  counted. 
Then  drop  down  to  the  next  row  of  spaces  and  continue  counting 
back  and  forth  in  the  same  manner  until  six  rows  of  six  spaces  each 
are  counted,  as  shown  in  Fig.  68.  Place  the  results  of  counting  on 
paper  in  the  same  relation  to  each  other  as  the  spaces  illustrated, 
as  follows: 


5 

6 

5 

4 

7 

5 

9 

6 

C, 

6 

6 

7 

4 

5 

5 

5 

8 

7 

7 

5 

8 

6 

4 

7 

6 

6 

7 

7 

9 

7 

6 

6 

6 

6 

5 

7 

37   +  34   +  37  +  34  +  39  +  40 
221  --  36  =  6/y. 


221 


Having  made  the  count,  the  slide  and  cover-glass  should  be  cleaned 
a.s  previously  described.    The  pipette,  which  has  been  left  in  a  hori- 


134  SPECIAL  PHYSIOLOGY 

zontal  position  in  a  safe  place,  should  be  rolled  again  for  three  minutes. 
Fill  the  counter  and  adjust  the  cover-glass  carefully  as  before;  count 
another  group  of  thirty-six  spaces  and  record  the  results  obtained. 
If  the  averages  of  the  two  counts  differ  more  than  one,  the  same 
procedure  must  be  carried  out  the  third  time,  and  the  average  of 
the  tvv'o  fields  nearest  alike  taken  and  the  estimate  made. 

To  compute  the  number  of  corpuscles  per  cubic  millimetre,  find 
the  average  number  of  cells  for  each  space  and  multiply  this  by 
4000,  as  each  space  is  2^  mm.  X  xo"  t^^^-  X  iV  ^J"^-  This  Tvill  give 
the  actual  number  of  cells  per  cubic  millimetre  in  the  diluted  blood. 
Then  make  the  correction  for  the  dilution  of  the  blood  by  multiplying 
by  100  or  200,  and  the  result  "^dll  be  the  number  of  red  cells  per 
cubic  milHmetre  in  the  specimen  of  blood  taken.  In  the  example 
given  above  it  would  work  out  as  follows: 

First  36  spaces,  63^;  second  36  spaces,  6|-|.  Average  of  the  two 
groups,  6^.  6iX  4000  -  2.5,000  X  200  =  5,000,000,'' the  number 
of  red  cells  per  cubic  millimetre. 

Precautions.  The  cement  used  on  the  counting  slide  is  dissolved 
by  alcohol  or  ether;  so  these  licpids  should  not  be  used  on  the  plate. 
Roll  the  filled  pipette  between  the  thumb  and  finger,  and  do  not 
shake  the  pipette,  as  some  of  the  solution  is  sure  to  be  lost.  A  com- 
mon source  of  error  that  can  easily  be  detected,  but  which  is  often 
overlooked,  is  the  unequal  distribution  of  cells  on  the  marked  plate. 
As  soon  as  the  drop  is  placed  on  the  marked  plate  the  cells  begin 
to  settle,  and,  of  course,  most  of  them  settle  where  the  drop  is  thickest, 
that  is,  in  the  center.  This  can  be  avoided  by  getting  the  cover- 
glass  in  place  quickly  and  making  the  whole  drop  of  an  even  thickness. 
Each  specimen,  before  being  coimted,  should  be  tested  to  see  that  the 
corpuscles  are  evenly  distributed  over  the  whole  drop.  For  the  same 
reason  the  filled  coimting  slide  should  be  kept  in  a  horizontal  position. 

Theoretically,  counting  the  cells  in  one  small  space  should  be 
suflBcient,  and  it  would  be  if  the  measurement  and  dilution  of  the 
blood  and  distribution  of  the  cells  were  all  perfectly  accurate.  This 
is  impossible,  and  the  errors  are  mostly  eliminated  by  the  methods 
given.  It  is  best  for  beginners  always  to  make  three  coimts  of  36 
spaces  each  from  the  same  pipette  and  take  the  average. 

Questions.  1.  ^Miy  is  alcohol  used  to  dry  and  not  to  clean  the 
pipette  ? 

2.  ^Vhy  should  the  marked  plate  be  dried  without  friction? 

3.  TMiat  does  hydrogen  peroxide  do  to  clean  the  pipette? 

4.  Why  rotate  the  needle  while  withdrawing  it  from  the  ear? 

5.  Why  wipe  away  the  first  drop  of  blood? 

6.  Why  wipe  the  end  of  the  pipette  before  piuting  it  into  the 
diluting  solution? 

7.  "Why  roll  the  pipette  as  the  blood  enters  the  bulb? 

8.  Why  blow  out  a  few  drops  before  putting  a  drop  on  the  slide  ? 


NORMAL  HEMATOLOGY  135 

9.  Why  draw  air  through  the  pipette  after  the  ether  is  drawn  out? 

10.  What  kind  of  a  sohition  should  be  used  to  dihite  the  blood; 
that  is,  what  properties  should  it  have? 

11.  Why  are  there  101  parts  in  the  pipette  instead  of  100? 

12.  Is  there  any  appreciable  variation  in  the  number  of  red  cells 
in  normal  individuals? 

13.  If  there  is  a  variation,  give  some  of  the  reasons. 

14.  Account  for  the  variations  observed  in  members  of  your 
section. 

B.  To  Count  the  White  Blood  Corpuscles. 

In  counting  the  number  of  white  cells  per  cubic  millimetre  in  the 
blood,  the  principle  of  diluting  and  counting  is  exactly  the  same  as 
in  counting  the  red  cells.  There  are  some  differences  in  the  details, 
since  we  must  first  get  rid  of  the  red  cells  so  that  the  white  cells  can 
be  seen,  and  because  of  the  small  number  we  must  dilute  less  and 
count  larger  areas. 

Appliances.  The  instruments  are  the  same,  with  two  exceptions 
or  modifications.  The  diluting  pipette  is  just  like  the  red-cell  diluting 
pipette,  except  that  it  is  larger  in  the  capillary  and  smaller  in  the 
bulb,  so  it  can  make  dilutions  of  ten  to  one  hundred  instead  of  one  to 
one  hundred.  The  counting  plate  should  have  the  modified  mark- 
ings as  shown  in  Fig.  68.  One  can  use  the  lower  power  (f )  objective 
of  the  microscope  just  as  well  and  save  time  by  it,  but  it  is  not 
necessary. 

Reagents.  The  same  as  when  counting  the  red  cells  except  that 
a  different  diluting  solution  must  be  used.  A  \  per  cent,  solution  of 
acetic  acid  in  distilled  water  will  destroy  the  red  cells  and  render  them 
invisible,  while  it  will  not  destroy  the  white  cells,  but  make  them  show 
more  plainly. 

White-cei>l  Diluting  Solution. 

Acetic  acid 0.5  c.c. 

Distilled  water         .         .         .        .         .     q.  s.  ad     100.0  c.c. 

Technique.  The  technique  of  obtaining  the  blood  and  filling  the 
pipette  is  the  same  as  with  the  red  cells,  except  that  the  capillary  tube 
is  so  large  that  we  must  have  more  blood.  For  this  reason  for  l)egin- 
ners  we  recommend  that  only  a  half-part  of  blood  be  taken  at  first. 
More  accurate  results  can  be  obtained  by  using  one  part,  but  much 
time  and  practice  is  necessary  to  fill  the  tube  easily.  The  capillary 
is  .so  large  that  .solutions  will  not  stay  in  it,  but  run  out  quickly  when 
the  tube  is  out  of  the  horizontal  position.  First,  then,  we  must  have 
more  blood;  usually  two  or  three  good-sized  drops  are  sufficient. 
Scc(jnd,  the  tube  must  be  held  horizontal  or  the  blood  and  solution 
will  run  out.  As  the  capillary  tube  is  large  it  is  very  easily  cleaned 
and   dried. 


136  SPECIAL  PHYSIOLOGY 

Roll  the  pipette  as  before  when  filled  and  in  a  few  moments  the 
mixture  will  turn  quite  dark;  when  it  no  longer  changes  color  it  is 
ready  to  be  counted.  Allow  a  few  drops  to  flow  out  of  the  tube  as 
in  the  case  of  the  red-cell  pipette,  then  place  a  small  drop  from  the 
end  of  the  pipette  on  the  ruled  plate.  It  is  not  necessary  to  blow 
the  fluid  out;  it  will  run  out.  Take  the  same  precautions  in  filling  the 
counter  and  adjusting  the  cover-glass  as  before,  except  that  there  is 
no  need  of  haste  in  placing  the  cover-glass,  because  the  white  cells  are 
lighter. 

Here,  because  we  have  a  clear  field  with  little  in  it,  and  the  cells 
are  quite  large,  we  can  use  a  lower  power  of  the  microscope  and  see 
a  whole  square  millimetre  at  once.  Begin  at  the  upper  left-hand 
corner  and  count  the  cells  in  each  space  1  mm.  square,  and  observe 
the  same  method  in  keeping  the  record  as  when  counting  the  red  cells. 
Clean  the  counting  slide,  roll  the  pipette  for  a  moment,  and  refill 
the  marked  plate  and  count  the  nine  spaces  again,  keeping  the 
records  as  before.  Do  this  at  least  three  times,  so  that  the  area 
counted  will  be  27  spaces,  each  1  mm.  square.  The  more  cells 
counted  the  more  accurate  the  results  should  be,  but  the  three  fields 
should  be  sufficient. 

To  estimate  the  number  of  cells  per  cubic  millimetre  in  the  blood 
specimen  used,  add  together  the  number  of  cells  and  divide  by  the 
number  of  millimetre  spaces  counted.  Each  space  is  -^q  mm.X  1  mm. 
X  1  mm.  or  y  q-  c.mm.  Now  multiply  the  average  number  of  cells  in 
each  space  by  10  to  find  the  number  of  cells  in  the  diluted  blood, 
and  then  by  10  or  20  according  as  the  blood  was  diluted,  and  that 
will  give  the  number  of  white  cells  per  cubic  millimetre  in  the  blood 
specimen,  as  follows: 


33 

45 

56 

47 

39 

57 

51 

43 

49 

48 

57 

39 

55 

45 

61 

37 

61 

53 

61 

53 

59 

43 

51 

41 

57 

39 

40 

142 

155 

154 

145 

135 

159 

145 

143 

142  =  1320 

1320  ^  27  =  48|X  10X20  =  9777^  white  cells  per  cubic  millimetre 
of  the  blood  examined. 

Questions.  1.  What  is  the  number  of  white  cells  per  cubic 
millimetre  in  the  blood  in  the  normal  individual? 

2.  What  is  the  normal  variation? 

3.  What  are  some  of  the  causes  of  the  variations? 

C.  To  Count  both  Red  and  White  Cells  at  the  Same  Time. 

In  general  the  whole  technique  is  followed  out  and  the  same 
instruments  used  as  when  counting  the  red  cells  alone.  The  method 
consists  of  using  a  diluting  solution  containing  a  stain  that  will  stain  the 
white  cells  only,  and  then  counting  the  red  and  white  cells  separately. 


NORMAL  H.EMATOLOGY  137 

Colored  Diluting  Solution. 

Methyl  violet 0.025  gram. 

Sodium  chloride 1.000  gram. 

Distilled  water 100.000  c.c. 

Count  the  red  cells  in  a  group  of  thirty-six  spaces  first,  and  keep 
the  record  as  before.  Next  count  the  white  cells  in  all  of  the  nine 
square-millimetre  spaces  and  keep  the  record  as  before.  This  should 
be  repeated  until  at  least  two  groups  of  red  cells  and  three  or  four 
groups  of  white  cells  are  counted  from  different  specimens  on  the 
counter,  and  each  record  should  be  kept  so  that  the  average  may 
be  taken  and  the  number  per  cubic  millimetre  be  estimated  in  each 
case. 

Estimate  the  number  of  cells  by  taking  the  average  and  estimating 
the  number  just  as  when  counting  the  red  cells  alone.  Estimate  the 
number  of  white  cells  just  the  same  as  before  by  taking  the  average 
for  each  y^o  c.mm.,  but  multiply  that  by  100  in  this  case  instead  of 
10  or  20,  as  the  blood  in  this  specimen  was  diluted  100  times. 

D.  Centrifugalization  of  the  Blood.     To  Determine  the  Relative 

Volume  of  Red  Corpuscles  and  Plasma.     To  Estimate  the 

Number  of  Red  Corpuscles  from  Their  Volume. 

Appliances.  Electric  or  hand  hsematocrit  (Fig.  67) ;  small  rubber 
tubing  to  fit  capillary  tube;  glover's  needle;  white  paper;  fine  wire 
for  cleaning  tubes. 

Reagents.     Di.stilled  water,  hydrogen  peroxide,  alcohol,  and  ether. 

Preparation.  Adjust  rubber  to  capillary  tube.  Put  empty  tube 
in  one  arm  of  cross-piece  to  preserve  balance.  Use  fine  wire  to 
remove  blood  from  the  capillary  tube,  then  clean  and  dry  as  other 
tubes. 

Technique.  Obtain  blood  from  the  lol)e  of  the  ear  as  heretofore 
described.  Draw  capillary  tube  full  of  blood.  Remove  the  rubber 
tube  by  pushing  it  off  and  not  by  pulling.  Remove  any  blood  from 
the  outside  of  the  capillary,  and  make  a  record  of  the  amount  of 
bloofl  in  the  capillary.  Place  the  tul)e  in  the  cross-piece  of  the 
instrument  as  quickly  as  possible  and  centrifugalize  at  least  three 
minutes  at  the  rate  of  7000  to  10,000  rotations  per  minute.  Take  out 
the  tube  and  lay  on  a  piece  of  white  paper  to  read  the  divisions. 
J)ach  degree  of  the  scale  is  estimated  to  contain  about  100,000  cells; 
hence,  a  tube  in  which  the  red  column  stands  at  .'jO  would  indicate 
about  .5,000,000  red  corpuscles  per  cubic  millimetre.  The  use  of 
this  instrument  is  designed,  however,  chiefly  to  show  the  volume  of 
red  rorpn-srlrs  rather  than  the  numher. 

Precautions.  Do  not  displace  the  rubl)er  i)ads  in  the  outer  ends 
of  the  rotating  arm,  as  the  blood  will  be  thrown  out  of  the  tube  and 


138  SPECIAL  PHYSIOLOGY 

necessitate  the  repetition  of  the  test.  Before  starting  each  test  see 
that  the  pads  are  in  place. 

If  the  tube  is  not  adjusted  in  the  apparatus  and  set  to  rotating 
within  a  few  seconds  after  the  blood  is  drawn,  coagulation  will  set 
in  and  hinder  the  complete  separation  of  the  corpuscles  from  the 
plasma.  Should  separation  not  be  complete  in  three  minutes  the 
test  should  be  repeated.  The  instrument  should  be  started  and 
stopped  gradually,  as  the  sudden  starting  and  stopping  injures  it. 

Questions.  1.  Determine  the  volume  percentage  of  red  blood 
corpuscles  in  a  number  of  normal  individuals. 

2.  Do  apparently  normal  individuals  have  the  same  or  approx- 
imately the  same  volume  percentage  of  red  blood  corpuscles  ?  If  not, 
seek  for  causes  of  the  variations  in  different  individuals. 

3.  Does  the  same  individual  have  the  same  volume  percentage  of 
red  blood  corpuscles  all  the  while? 

(a)  If  there  is  a  variation,  is  there  any  periodicity  to  be  observed? 
(6)  Seek  for  causes  of  any  variation  in  the  same  apparently  normal 
individual. 

4.  The  volume  percentage  as  recorded  by  the  hsematocrit  varies  with 
the  product  of  two  factors:  the  average  volume  of  the  individual 
corpuscles  by  the  number  of  corpuscles  per  unit  volume.    (F^vXn). 

(a)  Is  the  average  volume  of  the  individual  corpuscles  (v)  neces- 
sarily constant? 

(6)  If  it  is  not  constant,  would  one  be  justified  in  drawing  con- 
clusions regarding  the  number  of  corpuscle  per  unit  volume  (n)  after 
observing  the  volume  percentage  (F)  with  the  hsematocrit? 

5.  What  variation  of  the  observation  as  above  made  would  enable 
one  to  determine  with  reasonable  accuracy  the  number  of  corpuscles 
per  cubic  millimetre? 

6.  If  the  tube  were  only  partly  filled  at  first,  could  one  make  an 
accurate  test?     If  so,  tell  how  to  proceed. 


II.  THE  ESTIMATION  OF  THE  PERCENTAGE   OF  COLORING 
MATTER  IN  THE  BLOOD. 

The  estimation  of  the  coloring  matter  in  the  blood  is  based  on  the 
supposed  fact  that  a  normal  individual  under  normal  surroundings  has 
a  normal  amount  of  coloring  matter,  and  that  is  called  100  per  cent. 

The  instruments  that  have  been  devised  for  making  the  estimation 
are  numerous,  and  all,  while  theoretically  correct,  practically  are 
liable  to  a  greater  or  less  error  according  to  the  experience  and 
carefulness  of  the  observer.  They  are,  however,  in  a  skilful  and 
conscientious  operator's  hands,  quite  accurate,  and  are  especially 
so  when  used  to  compare  the  tests  of  the  same  patient's  blood,  week 
by  week. 


NORMAL  H^MA TOL OGY  139 

The  haemoglobin  contains  practically  all  the  coloring  matter,  and 
it  constitutes  90  per  cent,  of  the  red  cell.  The  haemoglobin  consists  of 
96  per  cent,  globulin  and  4  per  cent,  hsematin.  In  the  hsematin  is 
the  iron  of  the  corpuscles;  the  coloring  matter  of  the  blood  varies 
as  does  the  amount  of  iron.  Theoretically,  the  most  accurate  way 
to  test  the  haemoglobin  would  be  to  measure  the  amount  of  iron 
in  a  certain  amount  of  blood.  But  the  chemical  extraction  and 
weighing  of  so  small  an  amount  of  iron  is  too  difficult  and  tedious. 
Because  of  this,  other  tests  have  been  devised,  which  depend  upon 
the  observer's  eye  to  detect  the  likeness  of  shades  of  red  as  repre- 
sented by  the  blood  and  colored  glass,  solutions  or  paper.  Again,  the 
specific  gravity  of  the  blood  except  in  rare  cases  depends  upon  the 
amount  of  iron  in  the  red  cells,  and  varies  as  the  iron  does.  Then 
we  can  estimate  the  percentage  of  haemoglobin  by  finding  the  specific 
gravity  of  the  blood. 

The  principal  tests  may  be  classified  as  follows: 

1.  Estimation  of  iron  in  the  blood. 

JoUes'  ferrometer. 

2.  Estimation  of  percentage  of  coloring  matter  by  color  tests. 

A.  Fleischl's  haemometer. 

B.  Gowers'  haemoglobinometer. 

C.  Dare's  haemoglobinometer. 

D.  Tallquist's  haemoglobinometer. 

3.  Obtaining  the  specific  gravity  of  the  blood  by  Hammerschlag's 
method. 

A.  Fleischl's  Haemometer. 

Appliances.  Fleischl's  haemometer;  glover's  needle;  pasteboard 
tube  two  inches  in  diameter;  artificial  light;  small  beaker;  a  dark 
room  or  cupboard. 

Fleischl's  haemometer  consists  of  a  sliding  colored-glass  wedge 
which  moves  in  a  standard  underneath  a  cylindrical  metallic  cup, 
and  a  capillary  tube.  This  cup  is  divided  into  two  equal  com- 
partments and  has  a  glass  bottom  and  a  detached  glass  top.  The 
capillary  tube  is  very  small  and  is  held  by  a  small  metallic  band  on 
a  handle.  The  glass  wedge  and  the  capillary  tube  are  the  important 
parts  of  the  instrument  and  are  made  to  be  used  together.  There  is 
a  number  on  the  handle  of  the  capillary  tube,  indicating  its  capacity, 
and  this  same  number  is  stamped  on  the  top  of  the  standard;  also 
a  number  is  placed  on  the  end  of  the  sliding  frame  that  holds  the 
glass  wedge,  and  the  same  number  appears  on  the  base  of  the  standard 
of  the  instrument  to  which  it  belongs  (Fig.  69). 

Reagents.     Distilled  water  and  hydrogen  peroxide. 

Preparation.  Clean  metallic  cell  or  well  with  water  and  dry  with 
a  cloth  only  when  it  needs  it.  The  capillary  tube  should  be  cleaned 
with  water  and  hydrogen  peroxide,  and  then  with  water  again,  by 


140 


SPECIAL  PHYSIOLOGY 


waving  it  back  and  forth  in  the  sokitions  for  a  moment  or  two. 
Then  carefully  dry  the  tube  by  blowing  air  through  it,  holding  the 
tube  about  two  inches  from  the  mouth  so  as  to  avoid  the  moisture 
of  the  exhaled  air.  Fill  each  side  of  the  metallic  cup  about  three- 
fourths  full  of  distilled  water.  Prepare  the  needle  and  the  ear  or 
finger  as  in  other  tests. 

Technique.  Obtain  the  blood  in  the  usual  manner.  Hold  the  lobe 
of  the  ear  with  the  thumb  and  finger.  Use  the  second  drop.  Hold 
the  capillary  tube  horizontally  and  carefully  touch  the  drop  of  blood 
with  the  end  of  the  tube  onlv.    If  the  tube  is  clean  it  will  fill  rapidly 


Fig.  69 


Fleischl's  hsemometer. 


by  capillary  attraction.  If  there  is  any  blood  on  the  outside  of  the 
tube  or  air-bubbles  inside,  it  must  be  cleaned,  dried,  and  refilled 
properly.  If  the  capillary  is  overfull,  remove  the  excess  by  touching 
the  tip  to  a  cloth  or  filter  paper.  Then  quickly  put  the  capillary 
tube  into  the  water  in  one  compartment  of  the  metallic  cell  and  wave 
it  back  and  forth  or  up  and  down,  and  the  blood,  if  fresh  enough,  will 
readily  mix  with  the  water;  then  allow  a  few  drops  of  water  from  the 
medicine  dropper  to  flow  through  the  capillary  into  the  same  com- 
partment to  wash  the  blood  that  sticks  to  the  tube.  Now  fill  each 
compartment  almost  full  with  distilled  water,  taking  care  that  the 
contents  of  either  compartment  does  not  flow  into  the  other.    Take 


NORMAL  HEMATOLOGY  141 

the  handle  of  the  capillary  and  stir  the  one  that  contains  the  blood 
so  as  to  make  the  mixture  complete.  Now  carefullv  sUde  the  thick 
cover-glass  over  the  compartments  and  gradually  fill  each  cell  with 
water  as  the  cover-glass  is  put  on  until  there  is  no  air  left  in  either 
cell.  Exclude  dayhght  by  use  of  a  dark  room  or  a  cupboard,  and 
adjust  the  reflector  so  that  the  artificial  yellow  light  is  thrown  up 
through  the  diluted  blood  and  water  from  the  side  of  the  instrument, 
thus  placing  both  cells  in  same  relation  to  the  reflector  and  the  light. 
While  making  the  test  alwavs  shade  the  eves  from  the  light  bv  placinfir 
some  thick  paper  or  a  pasteboard  tube,  that  reaches  from  the  instru- 
ment to  the  forehead,  before  the  eyes.  It  is  better  to  use  only  one 
eye  at  a  time,  and  look  only  for  a  few  seconds  at  each  time,  gi^"ing 
the  eve  a  rest  and  a  chance  to  regain  the  abilitv  to  distinguish  tints. 
Stand  at  one  side  of  the  instrument  or  turn  the  instrument  so  as 
to  face  the  light  and  to  bring  the  two  cells  into  similar  relations 
with  the  eve.  Begin  with  a  glass  of  a  lighter  color  than  the  blood, 
and  move  the  colored-glass  shde  by  quick  turns  about  one-fourth 
of  an  inch  each  time  until  the  color  or  tint  of  the  diluted  blood  appears 
to  be  the  same  as  that  of  the  colored  slide;  then  make  the  reading. 
Next  turn  the  colored  glass  on  imtil  it  is  darker  than  the  diluted 
blood  and  do  the  same  as  before,  except  in  the  opposite  direction, 
turning  the  slide  until  the  color  of  the  glass  and  blood  are  the  same, 
and  then  make  the  reading.  Usually  the  first  reading  will  be  too 
low  and  the  second  too  high.  The  dift'erence  will  usually  be  about 
10  per  cent.  The  correct  result  will  be  between  these  two  readings, 
which  can  now  be  obtained  bv  carefullv  moving  the  glass  back  and 
forth  or  by  taking  the  middle  point  between  ihe  two  readings.  It  is 
almost  impossible  to  make  the  reading  accurately  and  honestly  unless 
great  care  is  taken,  and  the  writer  has  found  the  method  given  to 
produce  the  best  results  by  far.  This  method  should  be  practised  again 
and  again  and  done  with  care.  A  hasty  reading  is  rarely  correct. 
Repeat  the  whole  test  until  you  can  obtain  the  same  result  each 
time  with  the  same  individual's  blood. 

Precautions.  If  the  capillary  tube  is  not  perfectly  clean  it  will 
not  take  blood  by  capillary  attraction.  While  cleaning  the  tube 
always  test  it  by  touching  a  drop  of  water,  when  it  should  fill  imme- 
diately. This  will  save  time  and  ensure  quick  work.  The  amount 
of  blood  taken  is  so  small  and  this  is  diluted  so  much  that  the  least 
error  is  multiplied  many  times.  We  can  expect  accurate  results 
only  when  every  known  chance  of  error  is  safely  guardetl.  If  the 
capillary  has  moisture  or  foreign  matter  in  it,  the  tube  will  not  hold 
the  right  amount  of  bloo<l  and  the  result  will  be  too  small.  The 
bloo<l  must  be  obtained  and  mixed  in  the  metallic  cup  with  the 
water  ver\'  quickly,  or  it  will  clot  and  stick  in  the  capillar}-,  or  if  it 
does  leave  it  it  may  remain  as  a  clotted  thread  of  blood  in  the 
bottom    of    the    cell.      It    takes  a  little    practice   to    learn  to  wave 


142  SPECIAL  PH YSIOL OGY 

the  capillary  in  the  small  space  of  the  cell.  Very  gentle  constant 
waving  back  and  forth  or  into  the  water  and  out  is  the  most  effective 
in  getting  the  blood  out  of  the  tube.  Too  vigorous  movements  are 
liable  to  break  the  glass  tube.  When  completing  the  filling  of  the 
cells  with  water,  fill  the  cell  containing  water  only  first,  and  then 
there  is  no  danger  of  getting  any  of  the  diluted  blood  into  the  water 
compartment.  If  you  neglect  to  stir  the  blood  and  water  just  before 
adjusting  the  glass  cover  the  blood  will  remain  in  the  lower  part  of 
the  cup  with  the  water  on  top,  and  it  will  have  a  darker  color 
than  it  should  because  the  blood  really  is  not  diluted  as  necessary. 
This  will  give  a  higher  reading  than  is  accurate.  The  glass  cover 
should  always  be  used;  it  not  only  makes  the  amount  of  dilution 
accurate,  but  it  gives  an  even  surface  for  the  transmitted  light  rays. 
Without  the  glass  the  surface  of  the  water  is  either  concave  or  convex. 

The  metallic  cup  should  not  be  taken  apart  unless  it  is  very  dirty. 
If  the  glass  is  clean,  that  is  sufficient.  As  a  laboratory  precaution, 
where  several  instruments  are  in  use,  always  compare  the  markings 
to  be  sure  that  you  have  the  capillary  tube  that  goes  with  the  glass 
wedge  that  you  have. 

Questions.  1.  Why  use  distilled  water  to  dilute  blood  and  not  a 
saline  solution  similar  to  the  plasma  of  the  blood? 

2.  Name  four  common  sources  of  error  in  the  technique. 

3.  Can  different  individuals  make  approximately  the  same  reading 
of  the  same  test? 

4.  Can  different  individuals  make  approximately  the  same  results 
from  the  same  individual's  blood? 

5.  Does  every  individual  in  ordinary  health  have  the  same  per- 
centage of  haemoglobin? 

6.  How  would  you  explain  the  variation,  if  any? 

7.  Do  individuals  who  have  a  low  percentage  of  haemoglobin  have 
a  correspondingly  lessened  number  of  red  cells  per  cubic  millimetre? 

8.  Is  the  reverse  of  the  above  true? 

B.  Gowers'  Haemoglobinometer. 

Gowers'  hsemoglobinometer  consists  of  three  pieces:  a  capillary 
measuring  pipette,  a  graduated  tube,  and  a  sealed  tube  containing  a 
standard  colored  solution.  The  standard  colored  solution  represents 
the  color  of  1  per  cent,  solution  of  normal  blood.  The  graduated 
tube  is  marked  in  100  or  more  parts,  and  each  part  represents 
20  c.mm.  The  capillary  pipette  holds  20  c.mm.  up  to  the  mark  on 
the  tube.  If  the  blood  is  normal  it  will  be  necessary  to  add  water 
to  the  hundredth  mark  in  order  to  make  the  colors  correspond.  If 
the  blood  is  not  normal  the  percentage  can  be  read  off  the  graduated 
tube  at  the  top  of  the  diluted  blood  when  the  colors  correspond. 
There  are  two  kinds  of  instruments:    one  for  use  with  daylight,. 


NORMAL  HEMATOLOGY 


143 


which  has  a  white  substance  in  the  sealed  end  of  the  tube  containing 
the  colored  solution;  the  other  is  for  use  with  artificial  light  and  has 
a  black  substance  in  the  sealed  end  of  the  tube  (Fig.  70). 

Appliances.     Gowers'  hsemoglobinometer  and  a  glover's  needle. 

Reagents.     Distilled  water,  hydrogen  peroxide,  alcohol,  and  ether. 

Preparation.  Clean  the  instruments  in  the  usual  manner.  The 
capillary  pipette  should  be  cleaned  with  the  same  care  and  in  the  same 
way  as  the  diluting  pipette,  being  careful  to  first  clean  and  then  to 
dry  the  pipette.  Fill  the  graduated  tube  to  the  mark  20  or  30  with 
distilled  water;  prepare  the  needle  and  finger  or  ear  as  usual. 

Technique.  Obtain  the  blood  in  the  usual  way  except  that  a 
larger  quantity  of  blood  is  needed  than  for  the  preceding  instru- 
ment.     Hold  the  ear  in  the  same  way  and  fill  the  pipette  as  when 


Fig.  70 


Gowers'   bsemoglobinometer :  1,  blood  capillary;  2,  solution  of  standard  color;  3,  tube  in 
which  blood  is  diluted. 

obtaining  blood  in  the  pipette  for  counting  corpuscles.  Wipe  away 
the  first  drop  of  blood.  Touch  the  tip  of  the  pipette  to  the  drop  of 
blood,  resting  the  pipette  on  the  end  of  the  thumb,  which  is  behind 
the  ear,  and  slowly  suck  the  blood  up  to  the  mark  on  the  pipette, 
but  do  not  allow  the  blood  to  go  beyond  that  point.  If  the  drop  is 
not  sufficient,  quickly  obtain  the  second  drop  by  gentle  pressure 
high  above  the  wound  in  the  ear.  If  there  is  any  excess  of  blood 
on  the  point  or  sides  of  the  pipette,  fjuickly  wipe  it  away.  In.sert  the 
pipette  into  the  tube  almost  to  the  water  and  .slowly  blow  the  blood, 
drop  by  drop,  into  the  water.  Now  immediately  shake  the  tube  to 
mix  the  water  and  blood;  this  is  to  prevent  the  blood  clotting  or 
remaining  as  a  thread  in  the  bottom  of  the  tube.  Blood  still  remains 
in  the  capillary  on  its  sides;  so  fill  the  pipette  with  distilled  water  and 
blow  this  into  the  tube,  three  or  four  times.     Then  tlu)roiighly  mix 


144  SPECIAL  PHYSIOLOGY 

the  blood  and  water  by  shaking  or  rolhng  the  tube  gently.  Do  not 
place  the  thumb  over  the  end  and  shake,  as  an  appreciable  amount 
of  color  will  be  lost  and  a  foam  is  formed  that  delays  the  reading. 

Now  place  the  tube  in  the  rubber  block  beside  the  tube  containing 
the  standard  solution  and  add  distilled  water,  drop  by  drop,  to  the 
diluted  blood,  always  shaking  the  tube  between  the  additions  to 
keep  the  blood  and  water  well  mixed.  Continue  this  until  the  color 
of  the  blood  solution  is  not  darker  nor  lighter  than  the  standard 
solution.  The  comparison  of  the  colors  is  made  either  by  trans- 
mitted or  reflected  daylight.  The  eye  will  be  assisted  by  placing 
the  tube  behind  a  piece  of  white  paper  and  holding  them  toward 
the  window  light.  The  reading  is  made  directly  from  the  graduated 
tube,  in  percentage  of  haemoglobin  when  the  color  of  the  diluted 
blood  is  the  same  as  the  standard  solution.  Repeat  the  test  until 
the  same  result  is  obtained  continually. 

Precautions.  If  air  bubbles  are  drawn  up  into  the  capillary,  or 
if  it  is  either  over  or  underfilled,  the  tube  must  be  recleaned  and 
dried  and  the  test  repeated  until  done  accurately.  If  the  pipette 
contains  moisture  or  foreign  matter  the  measurement  will  not  be 
accurate.  Always  remove  any  blood  that  may  happen  to  get  on  the 
outside  of  the  pipette,  as  it  will  increase  the  result.  It  is  a  good  plan 
to  have  a  large  drop  of  blood  ready  before  you  begin  to  fill  the  pipette, 
rather  than  to  take  two  or  three  small  drops.  Because  of  the  time 
consumed  to  obtain  the  amount  of  blood  needed  there  is  liability 
of  the  blood  clotting  and  sticking  in  the  capillary.  When  only 
partially  clotted  the  blood  is  blown  into  the  graduated  tube  and 
remains  as  a  clotted  thread  in  the  bottom.  Gently  striking  the  finger 
against  the  tube  or  shaking  the  tube  sidewise  is  sufficient  to  mix 
the  blood  and  water,  and  is  far  better  than  placing  the  thumb  over 
the  mouth  of  the  tube  and  shaking  it  up  and  down.  If  this  latter 
method  is  used  it  will  make  a  difference  of  5  to  10  per  cent,  in  results. 
Always  be  sure  to  wash  the  capillary  out  a  number  of  times  and 
place  the  washings  in  the  graduated  tube,  or  the  result  obtained  will 
be  less  than  the  test  should  show.  If  a  tube  has  been  partially  or 
improperly  filled,  do  not  leave  it  so;  always  blowout  the  blood  before 
it  can  clot,  and  much  time  will  be  saved.  A  reading  should  be 
made  each  time  and  recorded  before  more  water  is  added,  for  if 
one  should  dilute  the  blood  too  much  and  had  no  record  of  the  last 
reading  the  test  is  spoiled  and  the  work  lost. 

C.  Dare's  Hsemoglobinometer. 

Appliances.  Dare's  hsemoglobinometer,  a  candle,  and  a  glover's 
needle. 

Preparation.  Dare's  instrument  estimates  the  percentage  of 
haemoglobin  by  comparing  the  color  of  a  thin  film  of  blood  of  a  cer- 


NORMAL  HEMATOLOGY  145 

tain  thickness  with  a  revolving  colored,  wedge-shaped  disk  of  glass. 
The  only  preparation  necessary  is  to  clean  and  polish  the  glass  plates 
that  hold  the  blood,  and  adjust  them  in  their  holder. 

Technique.  Obtain  a  good-sized  drop  of  blood  in  the  usual  man- 
ner. Touch  the  edge  of  the  plates  to  the  drop  of  blood,  and  the  space 
between  them  will  be  filled  with  blood  by  capillary  attraction.  Place 
the  holder  in  its  socket,  adjust  the  telescopic  tube  and  the  lighted 
candle,  and  make  the  reading  in  the  same  manner  as  with  the  Fleischl 
instrument.  A  dark  room  is  not  necessary,  but  it  is  well  to  hold  the 
instrument  toward  some  dark  object  as  a  background. 

D.  Tallquist's  Haemoglobinometer. 

Tallquist's  hfemoglobinometer  consists  of  a  chart  or  a  paper  on 
which  are  twelve  oblong,  red-colored  stripes,  ranging  from  10  to 
120  per  cent,  in  degree  of  color.  The  color  of  the  stripe  marked 
100  is  supposed  to  be  the  same  color  and  shade  as  that  of  a  piece 
of  filter  paper  in  which  there  is  normal  blood. 

The  other  stripes  vary  from  this  as  the  numbers  indicate. 

Appliances.  Tallquist's  haemoglobinometer  chart;  fine  Swedish, 
tightly  woven  filter  paper,  and  a  glover's  needle. 

Preparations.  Take  a  large  piece  of  light  yellow-colored  paper 
and  cut  an  oblong  hole  in  its  centre,  not  quite  as  large  as  one  of  the 
colored  stripes  on  the  chart.  Take  a  piece  of  the  filter  paper,  at 
least  twice  the  size  of  the  colored  stripes,  and  cut  a  straight  edge  on 
one  side  of  the  paper.    Prepare  the  needle  and  ear  as  usual. 

Technique.  Obtain  the  blood  in  the  usual  manner.  Take  the 
prepared  piece  of  filter  paper  and  allow  drop  after  drop  of  blood  to 
be  absorbed  into  the  paper  until  it  is  covered  with  blood  over  an 
area  as  large  as  one  of  the  colored  stripes  of  the  chart.  Put  on  just 
enough  blood  to  saturate  the  paper,  no  less  and  no  more.  If  there  is 
too  little  blood  on  the  filter  it  will  be  white  still  on  the  under  side. 
If  there  is  too  much  blood  on  the  paper  it  will  have  a  glistening  sur- 
face, and  later  will  clot  upon  the  paper.  This  must  be  prepared 
quickly  and  very  evenly  and  then  compared  with  the  colored  stripes 
of  the  chart  at  once.  It  will  be  noticed,  when  the  blood  is  first  put 
upon  the  filter  paper  and  is  still  fresh,  that  it  has  a  glistening  appear- 
ance, but  that  it  soon  loses  this  and  appears  dull  red  for  a  few  mo- 
ments, and  then  it  takes  on  a  darker  red  appearance  of  clotted  blood. 
The  time  to  take  the  reading  is  while  it  has  the  fresh,  dull-red 
color,  just  after  the  glistening  surface  has  disappeared  and  before  the 
dry,  darker  red  color  comes.  This  gives  only  a  few  moments  in  which 
to  make  the  reading.  Place  the  perforated  paper  on  the  colored  chart 
and  place  the  filter  paper  with  the  l)lo()d  right  next  to  the  oblong 
perforation.  The  examiner  must  control  his  inclination  to  manu- 
facture results.    This  is  best  accomplished  by  using  the  same  method 

10 


146  SPECIAL  PHYSIOLOGY 

as  with  the  Fleischl  instrument.  Do  not  allow  the  numbers  to  show. 
Begin  the  comparison  with  a  colored  stripe  much  lighter  than  the 
blood  specimen  and  move  up  one  stripe  at  a  time  until  the  colors 
appear  the  same;  then  make  a  reading.  Next  begin  with  a  stripe  of 
a  darker  color  than  the  blood  and  compare  colors  in  the  opposite 
direction  until  they  appear  the  same,  and  then  make  a  second  read- 
ing. The  correct  result  will  be  between  these  two  readings,  and 
usually  the  two  readings  will  be  10  or  more  per  cent,  apart.  The 
test  is  made  by  reflected  daylight.  It  is  well  to  have  a  good,  bright 
light,  although  direct  sunlight  is  not  good. 

Precautions.  The  amount  of  blood  that  the  filter  paper  will 
absorb  is  quite  constant,  and  yet  the  amount  that  can  be  put  on  to 
make  the  paper  red  is  variable.  If  you  take  long  enough  and  the 
blood  does  not  clot  quickly,  a  very  small  amount  of  blood  will  sat- 
ura,te  the  paper.  It  should  be  saturated  quickly  before  the  glistening 
effect  is  gone,  and  then  the  amount  is  quite  constant.  This  is  one  of 
the  greatest  errors  to  be  avoided,  and  necessitates  strict  and  accurate 
attention  to  details.  The  error  made  with  reading  is  the  same  as  with 
the  other  color  tests,  except  as  the  specimen  changes  color.  A  spot 
of  blood  1  cm.  in  diameter  is  not  large  enough  to  compare  with  the 
large  red  stripe  of  the  chart.  Colored  stripes  of  paper  of  equally  large 
size  can  be  more  accurately  compared  than  when  one  is  very  small; 
the  eye  is  overpowered  by  the  larger  amount  of  color.  Many  shades 
of  color  before  the  eye  at  one  time  are  confusing;  so  it  is  important 
that  all  colored  stripes  should  be  covered  except  the  one  being  used. 
The  above  common  errors  are  partly  responsible  for  the  disrepute  in 
which  the  method  is  held  in  the  minds  of  some  observers.  The 
errors  are  of  such  a  nature  that  the  accuracy  of  the  test  depends 
almost  entirely  upon  the  operator.  The  technique  is  easily  and 
quickly  performed,  but  the  beginner  should  repeat  the  test  until  he 
can  obtain  the  same  result  a  number  of  times  with  the  same  blood. 

The  filter  paper  containing  blood  is  wet  and  will  destroy  the  colored 
stripes  if  it  touches  them. 

E.  Estimation  of  Percentage  of  Haemoglobin  of  the  Blood  by 
Finding  the  Specific  Gravity. 

The  specific  gravity  of  the  blood  can  be  obtained  direct  from  a  quan- 
tity of  blood  as  with  other  solutions.  This  is  not  necessary,  because 
when  a  drop  of  any  fluid  is  put  in  another  fluid  of  the  same  specific 
gravity  that  the  drop  does  not  mix  with,  it  will  go  to  the  center  of  the 
latter  fluid  and  remain  there.  If  it  is  lighter  it  will  come  nearer  the 
surface,  and  if  it  is  heavier  it  will  sink.  There  are  a  number  of  solu- 
tions that  might  be  used.  One  of  the  most  accurate  is  sodium  sul- 
phate in  solution,  placed  in  different  cylinders  in  different  strengths. 

The  specific  gravity  of    the  blood,  except  in  some  cases,  as  in 


NORMAL  HEMATOLOGY  147 

leukaemia  and  dropsy,  varies  as  the  amount  of  iron  in  the  cor- 
puscles. It  must  therefore  be  evident  that  the  specific  gravity  of 
the  blood  varies  as  the  percentage  of  haemoglobin  varies.  By  con- 
sulting the  table  of  Hammerschlag,  given  below,  the  percentage  of 
haemoglobin  can  be  read  for  the  specific  gravity  of  the  blood  at  once. 
The  most  practical  solutions  to  use  for  finding  the  specific  gravity 
of  the  blood  are  benzole  and  chloroform,  because  of  the  ease  and 
speed  with  which  they  may  be  used. 

Table  of  Hammeeschlag. 


Specific  gravity.         Haemoglobin. 

Specific  gravity. 

HEemoglobin. 

1.033-1.035     =     25-30  per  cent. 

1.048-1.050      = 

55-65  per  cent. 

1.035-1.038     =     30-35    " 

1.050-1.053     = 

65-70    "       " 

1.038-1.040     =     35-40    "       " 

1.053-1.055     = 

70-75    "       " 

1.040-1.045     =     40-45    "       " 

1.055-1.057     = 

75-85    "       " 

1.045-1.048     =      45-55    "       " 

1.057-1.060     = 

85-90    "       " 

Appliances.  Specific  gravity  bulb  or  hydrometer;  a  quadrilateral 
or  cylindrical  graduated  glass  tube  about  six  inches  high;  a  pipette  or 
pointed  glass  rod;  a  stirring  rod,  and  a  glover's  needle. 

Reagents.  Those  for  cleaning  capillary  pipette,  graduated  tube, 
and  needle,  also  benzole  and  chloroform. 

The  hydrometer  is  a  glass  tube  containing  mercury  and  air,  and 
graduated  so  that  when  placed  in  distilled  water  at  room  temperature 
it  reads  1.000. 

Preparation.  Clean  all  the  apparatus  as  usual,  and  make  a  mix- 
ture of  V)enzole  and  chloroform  in  the  gla.ss  tube  of  a  specific  gravity 
of  about  1.060. 

Technique.  Secure  the  blood  in  the  usual  way.  Suck  at  least  three 
good-sized  drops  of  blood  into  the  pipette.  Now  before  the  blood 
clots  in.sert  the  point  of  the  pipette  into  the  .solution  and  blow  out  one 
or  two  drops  of  blood,  but  no  air.  If  the  drop  of  blood  goes  to  the 
center  of  the  mixture  and  remains  there  after  the  mixture  is  well 
stirred,  then  the  specific  gravity  of  the  blood  is  the  same  as  that  of 
the  mixture.  If  the  drop  comes  to  the  top  it  is  lighter  than  the 
mixture,  and  benzole  must  be  added  and  .stirred  in.  If  the  drop  goes 
toward  the  bottom  it  is  heavier  than  the  mixture,  and  chloroform 
mu.st  be  added.  Add  just  a  few  drops  of  benzole  or  chloroform  at  a 
time  and  stir  well  and  test  before  adding  more.  The  quickness  with 
which  the  testy4s  performed  depends  upon  the  carefulness  in  adding 
the  benzole  or  chloroform  and  in  keeping  the  mi.xture  stirred.  Repeat 
the  test  until  the  same  result  is  easily  and  cjuickly  obtained. 

Precautions.  The  blood  will  stick  to  whatever  it  comes  in  con- 
tuf-t  with,  the  sides  of  the  graduated  tube,  the  stirring  rod,  or  the 
specific  gravity  bulb,  if  they  are  not  clean  and  dry.  There  is  danger, 
when  the  pi[)ette  is  u.sed  to  obtain  the  blood,  of  blowing  small  air- 
bubbles  into  the  drop  as  it  is  put  into  the  .solution,  which  will  cause 
it  to  Moat.     If  the  mixture  is  lighter  than  the  blood,  the  drop  will  go 


148  SPECIAL  PHYSIOLOGY 

straight  to  the  bottom  and  adhere  with  the  force  of  the  fall.  The 
difficulty  with  the  pipette  can  be  overcome  easily  by  using  a  pointed 
glass  rod.  Secure  the  drop  of  blood  on  the  point  of  the  rod  and  shake 
it  off  into  the  solution.  The  benzole  and  chloroform  evaporate  very 
rapidly  and  change  the  specific  gravity  of  the  mixture.  The  two 
liquids  do  not  stay  mixed,  but  need  stirring  frequently.  Do  not 
attempt  to  work  with  the  same  drop  of  blood  more  than  two  minutes ; 
take  a  fresh  drop  and  continue.  Make  the  specific  gravity  of  the 
mixture  as  near  that  of  the  blood  as  possible  before  adding  the  second 
drop.  One  or  two  drops  will  always  determine  approximately  what 
the  specific  gravity  of  the  blood  is;  then  take  a  third  drop  and  prove 
it  exactly.  The  solutions  of  benzole  and  chloroform  can  be  put  into  a 
glass-stoppered  bottle  and  used  again;  so  there  is  little  waste  except 
from  evaporation.  This  is  one  of  the  best  tests  for  obtaining  the  per- 
centage of  haemoglobin,  as  the  personal  equation  is  largely  eliminated 
and  the  burden  of  accuracy  is  placed  upon  the  instrument. 
Questions.     1.  Why  make  the  mixture  1.060  to  begin  with? 

2.  What  is  the  specific  gravity  of  benzole?    Of  chloroform? 

3.  Why  are  they  better  than  other  solutions  for  a  quick  test? 


III.  EXAMINATION  OF  FRESH  BLOOD. 

A.  Coagulation  of  Normal  Blood. 

The  coagulation  of  normal  blood  is  a  phenomenon  that  takes  place 
quite  constantly  in  from  three  to  five  minutes.  But  in  disease  this 
time  may  be  prolonged  indefinitely.  The  coagulation  may  be  approx- 
imately tested  by  taking  a  large  drop  of  blood  on  a  warmed  slide,  and, 
while  holding  it  in  the  hand,  draw  through  the  drop  a  needle  or  a 
straw  from  an  ordinary  broom  every  quarter  or  half-minute,  and  note 
when  a  clot  follows  the  straw  out  of  the  drop.  Wright's  instrument 
for  testing  coagulation  is  slightly  more  accurate. 

Questions.     1.  What  is  coagulation? 

2.  What  becomes  of  the  corpuscles? 

3.  Is  there  any  variation  in  the  time  of  coagulation  among  the 
individuals  in  your  section? 

B.  Microscopic  Examination  of  Blood. 

The  microscopic  examination  of  fresh  and  stained  blood  is  of 
great  clinical  importance.  In  quite  a  number  of  diseases  it  gives  a 
specific  diagnosis  which  could  not  otherwise  be  gained. 

Appliances.  Microscope,  with  one-eighth  or  one-twelfth  oil- 
immersion  objective;  eye-piece  micrometer;  white  ground-glass  slides, 
seven-eighths  inch  square;  No.  1  cover-glasses;  glover's  needle,  and 
alcohol  lamp  or  Bunsen  flame. 


NORMAL  HEMATOLOGY  149 

The  micrometer  is  a  small  piece  of  glass  on  which  there  is  a  scale 
marking  off  equal  spaces.  This  is  placed  on  the  diaphragm  of  the 
eye-piece  of  the  microscope  and  put  in  focus  by  pushing  it  up  or 
down  as  needed.  The  scale  is  then  compared  with  a  stage  micrometer 
marked  in  microns  and  the  value  of  the  eye-piece  scale  thus  deter- 
mined. 

Preparation.  Wash  the  cover-glasses  and  slides  with  soap  and 
water  and  then  thoroughly  rinse  in  clean,  warm  water.  Polish  the 
glasses  with  a  clean,  soft  towel.  When  handling  the  slides  or  cover- 
glasses  hold  them  always  by  their  edges,  and  never  touch  a  flat  sur- 
face. Success  in  preparing  fresh-blood  specimens  depends  largely 
upon  the  absolute  cleanliness  of  the  glasses  used.  Before  using  the 
glasses  pass  them  through  the  Bunsen  or  alcohol  flame  six  or  eight 
times  w^hile  holding  them  with  the  fingers,  then  they  will  not  be 
broken.  Put  the  glasses  down  in  a  clean,  safe  place,  with  the  heated 
side  up,  as  this  is  the  side  to  be  used. 

Technique.  Obtain  the  blood  as  before,  using  the  second  or  third 
drop.  Bring  one  of  the  previously  heated  cover-glasses  underneath 
the  drop  of  blood  and  allow  it  to  just  touch  lightly  the  center  of  the 
glass;  then  quickly  place  the  cover-glass,  blood  side  down,  upon  a 
glass  slide.  If  the  glasses  are  clean,  the  blood  fresh  enough,  and  of 
the  right  amount,  the  blood  will  spread  out  into  a  thin  layer,  in  which 
the  corpuscles  lie  on  the  flat  surface  in  a  single  layer.  Around  the 
margin  the  cells  will  be  more  or  less  grouped  together.  The  specimen 
should  then  be  placed  under  the  microscope  and  studied  at  once. 
Mix  a  small  drop  of  blood  with  a  small  drop  of  water  on  a  slide  and 
cover  with  a  cover-glass  and  examine.  Smear  a  drop  of  blood  on  a 
slide  by  drawing  another  slide  over  it,  cover  one  with  a  glass,  and 
make  another  and  leave  uncovered,  and  examine. 

Precautions.  It  is  very  important  that  the  slides  and  cover- 
glasses  should  be  kept  perfectly  clean  and  dry.  If  alcohol  is  used  an 
alcoholic  residue  is  left  upon  the  glass  and  often  interferes  with  the 
examination.  Touching  a  glass  surface  with  a  freshly  cleaned  finger 
will  leave  enough  fat  and  dirt  to  prevent  the  blood  spreading.  The 
blood  must  be  transferred  to  the  glasses  and  covered  quickly,  or  it 
will  partially  clot  and  prevent  spreading.  The  drop  must  be  large 
enough  to  give  a  thin  clean  field  of  at  least  one-half  inch  in  diameter, 
but  it  must  not  be  so  large  that  the  blood  cannot  spread  out  into  a  thin 
film  between  the  glasses.  The  spreading  must  take  place  entirely  by 
capillary  attraction;  pressure  must  never  be  used  to  continue  or  cause 
sprea(h"ng.  The  ghiss  must  touch  only  the  tip  of  the  drop  while 
obtaining  the  blood;  if  it  touches  the  ear  the  blood  will  not  spread. 

Questions.     Red  Cell.      1.   Describe  a  red  cell. 

2.   What  is  the  sliaj^e  of  a  red  cell? 

.':{.  How  may  the  shape  of  a  red  cell  be  demonstrated? 

4.  Are  the  red  cells  nucleated? 


150  SPECIAL  PHYSIOLOGY 

5.  What  are  the  dimensions  of  the  red  cells? 

6.  Are  there  any  variations  in  the  size  of  the  red  cells? 

7.  What  are  the  maximum  and  minimum  dimensions? 

8.  What  percentage  are  large,  normal,  or  small? 

9.  How  may  the  elasticity  of  the  red  cells  be  demonstrated? 

10.  What  are  the  causes  of  the  movements  of  the  red  cells? 

11.  How  are  the  red  cells  arranged? 

12.  What  causes  crenation? 

13.  What  causes  vacuolation? 

14.  How  large  are  blood  platelets? 

15.  What  happens  to  the  red  cells  in  the  presence  of  water? 

16.  What  happens  to  the  red  cells  while  drying  in  the  air? 

17.  What  happens  to  the  red  cells  when  spread  by  pressure? 

18.  Of  what  does  a  red  cell  consist? 
White  Cell.     1.  Describe  a  white  cell. 

2.  How  can  the  shape  of  a  white  cell  be  demonstrated? 

3.  How  can  you  demonstrate  the  elasticity  of  a  white  cell? 

4.  How  can  you  demonstrate  the  nucleus  of  a  white  cell? 

5.  What  are  the  dimensions  of  a  white  cell? 

6.  Are  there  any  variations  in  the  size  of  a  white  cell? 

7.  What  are  the  percentages  of  the  various  sizes? 

8.  Do  they  float  readily  under  the  cover-glass? 

9.  What  becomes  of  the  white  cell  in  the  presence  of  water? 

10.  What  becomes  of  the  white  cell  while  drying  in  the  air? 

11.  Of  what  does  a  white  cell  consist? 

C.  Spreading  Blood  for  Staining. 

Glass  Slide  Method.  Take  one  of  the  carefully  prepared  glass 
slides  and  allow  the  drop  of  blood  to  touch  it  near  one  end,  as 
shown  in  Fig.  71.  Place  this  on  a  table  and  hold  the  glass  by 
placing  a  finger  on  the  slide  beyond  the  drop  of  blood,  as  shown  in 
figure.  Then  take  a  ground-glass  slide,  hold  by  the  edge  between 
the  thumb  and  fingers  of  the  other  hand,  and  place  the  edge  of  one 
end  between  the  drop  and  the  finger  holding  the  slide,  as  shown  in 
figure.  Now,  with  a  free-arm  movement  from  the  shoulder,  quickly 
sweep  the  second  slide  across  the  remainder  of  the  surface  of  the 
first  slide,  exerting  a  very  slight  but  even  pressure;  the  resulting 
smear  will  be  as  shown  in  lower  slide  of  figure. 

The  speed  can  be  made  slowly  by  exerting  more  pressure,  but  it 
will  not  give  a  thin,  even  film  of  blood,  and  it  will  distort  the  cor- 
puscles more.    Make  a  number  of  smears  for  further  use. 

Cover-glass  Method.  Take  a  cover-glass  between  the  thumb 
and  first  finger  of  each  hand,  with  the  heated  surface  up  in  the  left 
and  the  heated  surface  down  in  the  right  hand,  as  shown  in  Fig.  72. 
Allow  the  center  of  the  glass  in  the  left  hand  to  just  touch  the  fresh 


NORMAL  HEMATOLOGY 


151 


drop  of  blood,  as  shown  in  Fig.  73.     Next,  quickly  drop  the  cover- 
glass  in  the  right  hand  on  the  drop  of  blood,  placing  the  glasses 


Fig.  71 


Showing  method  of  spreading  for  examination  of  fresh  blood. 
Fig.  72 


Fig.  73 


Showing  the  way  to  hold  the  cover-glasres. 


Touching  the  cover-glass  to 
the  blood  drop. 


together,  .so  that  each  comer  will  be  free,  as  shown  in  Fig.  74.  This 
is  easily  done  by  bringing  the  thumbs  clo.sely  together  and  holding 
the  cover-gla.ss  in  just  the   proper   position  before   letting  it  drop. 


152 


SPECIAL  PHYSIOLOGY 


The  blood  will  then  spread  between  the  surfaces  of  the  glasses  by 
capillary  attraction.  As  soon  as  the  blood  has  entirely  stopped 
spreading,  take  firm  hold  of  the  upper  glass  by  the  projecting 
corner  with  the  thumb  and  first  finger  of  the  right  hand,  on  the  flat 
surface  this  time,  as  shown  in  Fig.  75.  Now,  with  a  quick,  full  swing 
of  the  whole  arm,  pull  the  upper  glass  away  from  the  lower  one  as 
quickly  as  possible.  Always  pull  the  glass  away  in  the  same  plane 
it  was  in,  and  do  not  tilt  one  glass  upon  the  other,  otherwise  the 
spread  will  show  ridges  and  will  be  of  no  use.  Make  a  number  of 
specimens  for  further  .study. 

Fixing  Blood  Films.  After  the  blood  is  spread  the  glasses  are 
to  be  placed  under  a  bell  jar,  with  blood  side  upward,  and  allowed 
to  air-dry  until  perfectly  dry.  The  length  of  time  for  drying  depends 
upon  the  thickness  of  the  film;  usually  five  to  fifteen  minutes  are 
sufficient.  The  method  of  fixing  blood  spreads  may  be  divided  into 
two  classes:  chemical  and  thermal. 


Fig.  75 


Dropping  cover-glass  upon  the 
drop  of  blood. 


Showing  manner  of  holding  the  cover-glas 
to  jerk  them  apart. 


The  principal  chemicals  are  absolute  alcohol  and  ether,  abso- 
lute alcohol,  ether,  95  per  cent,  alcohol,  and  1  per  cent,  formal- 
dehyde. The  heating  or  baking  method  may  be  done  crudely 
by  passing  the  spread  back  and  forth  through  the  Bunsen  flame 
for  five  minutes,  while  being  held  with  the  fingers.  There  are 
also  copper  ovens,  copper  plates,  and  copper  receptacles,  con- 
taining water,  used  to  bake  the  blood.  For  staining  with  the 
ordinary  histological  or  bacteriological  stains  the  chemical  method 
of  fixing  is  sufficient,  but  when  some  of  the  finer  differential  staining 
is  desired,  as  with  the  Ehrlich  triacid  stain,  the  baking  method  is 
necessary,  and  a  copper  oven  controlled  by  a  thermostat  is  the  best. 
Fifteen  to  thirty  minutes  is  the  time  required  for  baking,  with  the 
temperature  about  100°  C.  The  time  depends  upon  the  thickness 
of  the  film.  Some  observers  employ  higher  temperatures  with  suc- 
cess. With  the  film  on  the  slide,  the  blood-fixing  jar  is  convenient  for 
the  chemical  method.  It  is  a  quadrilateral  jar,  wide  enough  to  allow 
four  or  five  slides  to  stand  in  the  jar,  with  a  ridge  of  glass  between 


NORMA  L  H^MA  TO  LOGY  1 53 

each  slide.  After  removing  them  from  the  fixing  solution,  the  speci- 
mens must  be  air-dried  under  a  bell  jar  until  all  the  solution  is  com- 
pletely evaporated. 

D.    Staining  Blood  Films. 

There  are  many  stains  that  may  be  used  to  stain  the  blood  cor- 
puscles. The  choice  of  stain  depends  largely  upon  the  purpose  of 
the  staining.  For  ordinary  histological  purposes  eosin  and  haema- 
toxylin  are  the  best. 

Technique  (1).  Fix  the  blood  film  in  alcohol  fifteen  minutes,  dry, 
and  stain  with  1  per  cent,  aqueous  eosin  in  50  per  cent,  alcohol  for 
two  minutes,  and  then  counterstain  with  Delafield's  hsematoxylin  for 
a  half-minute.  ^Yash  in  water,  allow  to  air-dry,  and  then  mount  in 
balsam.  But  for  finer  work,  when  parasites  are  suspected,  as  the 
Plasmodium  malarise,  or  when  a  differential  count  of  the  white  cells 
is  desired,  eosin  and  methylene  blue  are  necessary. 

Technique  (2).  Just  the  same  as  the  above,  except  that  a  10  per 
cent,  methylene  blue  in  50  per  cent,  alcohol  is  used  instead  of  the 
heematoxylin. 

Technique  (3).  The  other  stain  mentioned,  Ehrlich's  triacid,  con- 
tains both  acid  and  basic  stains,  and  stains  all  structures,  differen- 
tiating each.  In  special  diseases  of  the  blood  this  is  the  best  stain, 
for  among  its  other  advantages  it  differentiates  the  nucleus  of  a  red 
cell  from  that  of  a  white  cell. 

All  blood  films  must  be  fixed  carefully  by  heat,  preferably  in 
the  oven.  Allow  the  stain  to  remain  on  the  glass  for  four  or 
five  minutes;  then  wash,  air-dry,  and  mount  in  balsam  as  usual. 
The  stain  must  be  of  the  best  quality  and  accurately  prepared. 
Then  the  staining  depends  largely  upon  the  baking.  An  under- 
heated  or  overheated  specimen  will  not  stain  well;  the  first  will  appear 
too  red  from  the  acid  fuchsin,  and  the  latter  will  be  a  pale-lemon 
color  from  the  orange  G.  stain. 

E.    Differential  Counting  of  the  Cells. 

Appliances.  Blood  films  stained  with  eosin  and  methylene  blue 
or  triacid  stain;  microscope,  with  one-eighth  or  one-twelfth  oil- 
immersion  oVjjective  and  a  mechanical  .stage. 

Technique.  The  stained  blood  film  should  have  a  space  at  least 
one-half  inch  square  in  its  center  in  which  the  corpuscles  do  not  over- 
lap each  other.  Place  the  film  in  focus  with  the  microscope  and 
begin  at  the  upper  left-hand  corner  of  the  specimen.  Count  all 
the  various  kinds  of  white  cells,  and  keep  a  record  of  the  miniber 
of  each  kind  counted.  Next  count  all  the  red  cells  in  the  field,  and 
keep  a  record  of  the  number  and  also  of  any  peculiar  forms  and  their 


154  SPECIAL  PHYSIOLOGY 

number.  By  the  scale  on  the  mechanical  stage,  measure  the 
width  of  the  microscopic  field  and  then  move  the  specimen  to  the 
next  field  to  the  right.  Count  and  keep  a  record  of  all  the  various 
corpuscles  in  this  field.  Continue  counting  each  field  to  the  right  until 
across  the  specimen;  then  drop  down  to  the  next  row  of  microscopic 
fields  and  count  to  the  left,  and  so  on  until  the  whole  specimen  has 
been  counted  and  a  record  of  the  various  corpuscles  on  the  specimen 
has  been  obtained.  Usually  there  are  not  enough  white  cells  on  one 
specimen  to  take  an  average  from;  in  that  case  continue  counting 
specimens  until  at  least  100  white  cells  in  all  have  been  counted. 
They  normally  occur  in  the  percentages  as  given  in  the  table  below. 
If  there  is  difficulty  in  keeping  the  microscopic  field  because  it  is 
round,  take  a  piece  of  stiff  paper  and  cut  a  square  hole  in  it  just  the 
size  to  make  the  field  square,  and  place  the  paper  on  the  diaphragm 
in  the  eye-piece  of  the  microscope. 

Corpuscles  of  Normal  Blood. 

1.  Red,  5,000,000  per  cubic  millimetre.  A  biconcave  disk  7.7 
microns  in  diameter. 

2.  White,  8000  per  cubic  millimetre. 

Classification  of  Leukocytes. 

I.  Small  Mononuclear.  Irregularly  spherical,  8  to  10  microns 
in  diameter;  20  to  30  per  cent,  of  white  cells.  The  nucleus  nearly 
fills  the  cell  and  may  or  may  not  stain  deeply  blue  according  to 
technique,  though  it  usually  stains  well.  The  protoplasm  forms  a 
thin  rim  around  the  nucleus,  stained  faintly  blue. 

II.  Large  Mononuclear.  Irregularly  spherical,  12  to  13  microns 
in  diameter,  4  to  8  per  cent,  of  white  cells.  The  nucleus,  about 
half  the  size  of  the  cell,  lies  eccentrically,  takes  the  blue  stain  lightly, 
and  is  surrounded  by  protoplasm  very  faintly  blue,  with  the  layer 
next  the  nucleus  being  almost  unstained. 

Transitional  Forms.  Same  as  above,  except  that  the  nucleus  is 
indented  or  horseshoe-shaped. 

III.  Polynuclear.  (a)  Neutrophile.  Irregularly  spherical,  12 
to  14  microns  in  diameter;  60  to  70  per  cent,  of  white  cells.  Two 
or  more  nuclei  in  an  irregular  group.  Nuclei  are  stained  clearly. 
Protoplasm  is  partially  filled  with  fine  granules  that  stain  red  or 
pink,  with  a  bluish  or  pinkish  background. 

(6)  Eosinophile.  Irregularly  spherical,  12  to  14  microns  in 
diameter;  i  to  4  per  cent,  of  white  cells.  Two  or  more  nuclei,  faintly 
stained.  Protoplasm  is  filled  with  coarse  granules  stained  a  bright 
red  with  pinkish  or  unstained  background. 


fiff/ 


fiffH. 


Figni 


Fuj.vm 


a         "         C 


e     ^'     ^    /^        ^        «/  ^      i         ^ 


^V 


Y  JNZ  Cr*A:i£ 


BLOOD. 

(Ehrlich  triple  stain.) 
(Prepared  by  Dr.  I.  P.  Lyon.) 

Kig.  I.     TYPES   OF   LEUCOCYTES. 

a.  Polymorphonuclear  Neutrophile.  b.  Polymorphonuclear  Eosinophile.  c.  Myelocyte 
(Neutrophilic),  d.  Eosinophilic  Myelocyte,  e.  Large  Lymphocyte  (large  Mononuclear). 
/.  Small  Lymphocyte  (small  Mononuclear). 

Fig.  n.     NORMAL    BLOOD. 
Field  contains  one  neutrophile.     Reds  are  normal. 

Fig.  III.     ANEMIA,  POST-OPER.\TIVE  (secondary). 

The  reds  are  fewer  than  normal,  and  are  deficient  in  haemoglobin  and  somewhat 
irregular  in  form.  One  normoblast  is  seen  in  the  field,  and  two  neutrophiles  and  one 
small  lymphocyte,  sho%ving  a  marked  post-hsemorrhagic  anaemia,  w^ith  leueocytosis. 

Fig.  IV.     LEUCOCYTOSIS,  INFLAMMATORY. 

The  reds  are  normal.  A  marked  leueocytosis  is  shown,  with  five  neutrophiles  and 
one  small  lymphocyte.  This  illustration  may  also  serve  the  purpose  of  showing  the 
leueocytosis  of  malignant  tumor. 

Fig.  V.     TRICHINOSIS. 
A  marked  leueocytosis  is  shown,  consisting  of  an  eosinophilia. 

Fig.  VI.     LYMPHATIC  LEUKEMIA. 

Slight  anaemia.  A  large  relative  and  absolute  increase  of  the  lymphocytes  chietly 
the  small  lymphocytes)  is  shown. 

Fig.  VII.     SPLENO-MYELOGENOUS   LEUKEMIA. 

The  reds  show  a  secondary  anaemia.  Two  normoblasts  are  shown.  Tho  h^ucocytosis 
IS  massive.  Twenty  leucocytes  are  shown,  consisting  of  nine  neutrophiles,  seven  myelo- 
cytes, two  small  lymphocytes,  one  eosinophile  (polymorphonuclear)  and  one  eosinophilic 
myelocyte.  Note  the  polymorphous  condition  of  tho  leucocytes,  i.e.,  thoir  variations 
from  the  typical  in  size  and  form. 

Fig.  VIII.     VARIETIES   OF    RED   CORPUSCLES. 

n.  Normal  Red  Corpu.scle  (normocyte).  6,  c.  Aneemic  Red  Corpusclt^s.  (/-;/.  Poikilocytes. 
A.  Mlcroeyte.  i.  Megalocyte.  J-n.  Nucleated  Rod  Corpuscles.  j,k.  Normoblust.s.  /.  Micpo- 
blJist.    m.n,  Mogaloblasts. 


NORMAL  Hu^MATOLOGY  155 

IV.   STAINING  BONE-MARROW. 

Appliances.  A  strong  vice;  saw;  microscope,  with  one-fifth  to 
one-eighth-inch  objective;  fresh  hone  containing  red  marrow;  shdes, 
cover-glasses,  with  usual  equipment  necessary  for  fixing  and  staining 
films. 

Technique.  Place  the  bone  in  the  vice  and  fasten  it  just  suffi- 
ciently to  hold  it  for  the  saw.  Saw  off  an  end  and  then  close  the 
vice  on  the  bone  and  crush  it  enough  to  make  the  marrow  leave 
the  bone.  As  soon  as  the  drop  of  bone-marrow  forms,  touch  a  clean 
glass  slide  to  it  and  make  a  spread  by  the  slide  method.  Make  two 
or  three  spreads  so  as  to  be  sure  to  have  a  good  one.  Then  fix  and 
stain  as  with  the  blood  films,  using  either  eosin  and  methylene  or 
the  triacid  stain. 

Precautions.  The  bone  should  be  as  fresh  as  possible.  The 
piece  should  be  sawed  just  before  using  so  as  to  have  a  freshly  cut 
surface  from  which  to  take  the  marrow.  The  spread  is  apt  to  be 
too  thick.  Use  just  as  much  care  in  cleaning  the  slides  and  making 
the  spreads  as  when  making  the  blood  films. 

Questions.  1.  Name  and  describe  the  different  cells  found  in 
the  red  bone-marrow. 

2.  Are  there  cells  found  here  that  are  not  found  in  the  normal 
blood? 

.3.  What  is  the  difference  between  a  myelocyte  and  a  leukocyte 
of  the  same  size? 

Corpuscles  of  Red  Bone-marrow.  Red  Cells.  Normocyte,  non- 
nucleated,  G  to  8  microns  in  diameter;  normoblast,  nucleated,  6  to 
8  microns  in  diameter;  microcyte,  non-nucleated,  4  to  6  microns  in 
diameter;  microhlast,  nucleated,  4  to  G  microns  in  diameter;  7nef/alo- 
cyte,  non-nucleated,  8  to  10  microns  in  diameter;  megalohlast, 
nucleated,  8  to  10  microns  in  diameter;  poikilocyte,  non-nucleated, 
distorted. 

White  Cells.     Same  as  those  in  normal  blood. 

Myklocytes.  (a)  Neutrophile.  Irregularly  spherical,  10  to 
20  microns  in  diameter.  It  has  a  single  or  partially  divided  nucleus, 
nearly  filling  the  cell,  and  stained  a  pale  blue.  The  protoplasm  is 
filled  with  neutroj)hile  (fine)  granules  stained  a  bluish  red. 

(h)  Eoffinopliilc.  Same  as  above,  except  the  nucleus  is  less 
distinct  and  the  protoplasm  is  filled  with  coarse  granules  stained 
a  bright  red. 


CHAPTER   VI. 
DIGESTION  AND  ABSOEPTION. 

DIGESTION. 

As  stated  in  the  Introduction,  it  is  taken  for  granted  that  by  the 
time  a  medical  school  has  found  the  conditions  propitious  for  the 
establishment  of  a  laboratory  of  experimental  physiology,  the  whole 
province  of  chemical  physiology  will  have  been  occupied  by  the 
department  of  chemistry  as  a  legitimate  growth  of  that  department. 

The  American  laboratory  of  experimental  physiology  will  present 
almost  exclusively  the  physical  problems  of  physiology.  But  even 
where  such  are  the  conditions,  it  may  seem  advisable  to  introduce 
into  a  course  of  lectures  or  recitations  on  the  physiology  of  digestion 
a  series  of  demonstrations. 

The  following  exercises  in  the  chemistry  of  digestion  and  the 
physics  of  absorption  may  be  given  either  as  demonstrations  or  as 
laboratory  exercises. 

This  chapter  is  not  intended  as  a  substitute  for  any  of  the  excellent 
treatises  now  used  in  medical  schools,  but  rather  as  a  supplement 
to  them. 

It  will  be  taken  for  granted  that  the  student  has  had  at  least  one 
year  of  chemistry  before  he  enters  upon  this  course. 

To  give  the  course  which  is  outlined,  one  will  need  the  following 
apparatus  and  reagents: 

1.  Appliances,  (a)  Glassware  Utensils,  etc.  10  evaporating  dishes, 
assorted  sizes;  10  filters,  assorted  sizes,  5  cm.  to  20  cm.;  100  test- 
tubes,  15  cm.;  10  beakers,  30  c.c;  10  beakers,  assorted,  50  c.c.  to  2 1.; 
10  50-c.c.  graduated  cylinders;  4  graduated  cylinders,  100  c.c,  200 
c.c,  500  c.c,  1000  c.c;  3  Wedgewood  mortars,  2f,  4,  and  7  inches 
in  diameter;  filter  papers;  labels;  pig-bladders;  thread;  rubber  tubing, 
and  glass  stirring  rods. 

(6)  Apparatus.  Bunsen  burners,  with  rubber  tubing;  filter  stand; 
2  supports,  with  rings  and  gauze;  dialyzers;  1  incubator;  drying 
oven;  meat  hasher;  desiccator;  water-baths;  platinum  dishes,  15 
cc  to  100  c.c. 

2.  Reagents.  Diluted  iodine,  Fehling's  solution,  sodium  hydrate 
and  potassium  hydrate,  copper  sulphate,  distilled  water,  6  thistle 
tubes,  neutral  litmus,  concentrated  nitric  acid,  strong  ammonia, 
acetic  acid,  osmic  acid  (1  per  cent.),  pure  standard  pepsin,  muriatic 
acid  (c  p.,  sp.  gr.  1.16  =  31.9  per  cent.  abs.  HCl),  absolute  alcohol. 


DIGESTIOX  AND  ABSORPTION  ]  57 

ether,  chloroform,  calcium  chloride,  25  per  cent,  solution  XaOH, 
25  per  cent,  solution  KOH,  and  one-half  saturated  solution  XajCOg. 
Xon-medicated  absorbent  cotton  for  rapid  filtering  of  mucilaginous 
or^albuminous  liquids. 


I.   THE  CARBOHYDRATES. 

1.  Materials.  Potato  starch,  dextrin,  dextrose,  malto.se,  lactose, 
saccharose,  and  cellulose,  represented  by  absorbent  cotton  and 
ashless  filter  paper. 

2.  Preparation.  (1)  To  Prepare  Fehling's  Solution,  (a)  Into  a  half- 
litre,  glass-stoppered  bottle  put  34.64  grams  CuSO^,  c.  p.,  and  enough 
HjO  dist.  to  make  500  c.c.    Label  the  solution:  Fehling's  Solution  (a). 

(6)  Into  a  similar  receptacle  put  173  grams  of  potassic-sodic  tartrate, 
KNaC,H,0  +  4H20  (Rochelle  salt),  and  50  grams  of  NaHO,  weighed 
in  sticks;  add  enough  water  to  make  500  c.c.  Label:  Fehling's 
Solution  (b).  For  use,  mix  these  solutions  in  equal  parts.  A  con- 
venient quantity  for  the  following  experiments  is  100  c.c.  of  each 
solution. 

(2)  Prepare  a  starch  paste  by  rubbing  1  gram  of  starch  to  a  creamy 
consistence  with  water,  add  100  c.c.  of  distilled  water,  and  boil. 

(3)  Prepare  a  dilute  solution  of  iodine  by  direct  solution  in  water 
or  by  diluting  an  alcoholic  solution. 

3.  Experiments  and  Observations.  (1)  Put  a  little  dry  starch 
into  an  evaporating  dish;  add  some  dilute  iodine.  The  starch  turns 
blue.  Pour  a  few  drops  of  starch  paste  into  a  test-tube;  add  a  few 
drops  of  iodine.  Iodine  may  be  used  to  detect  the  presence  of  raw 
or  of  cooked  starch. 

(2)  Put  some  raw  starch  into  a  test-tube  or  beaker;  add  water  and 
stir.  The  starch  does  not  seem  to  be  at  all  soluble  in  water.  Stir 
or  shake  the  mixture  to  bring  the  starch  into  suspension  in  the  water; 
pour  upon  a  filter.  A  clear  filtrate  passes  readily  through.  Test 
the  filtrate  for  starch;  result,  negative;  pour  a  few  drops  of  iodine 
upon  the  filter,  starch  present.     Conclusions: 

(a)  Potato  starch  is  insoluble  in  cold  water. 

(h)  The  granules  of  potato  starch  will  not  pass  through  common 
filter  paper. 

(3)  Dilute  a  few  centimetres  of  .starch  pa.ste;  pour  it  upon  a  filter; 
to  the  filtrate  add  iodine.  The  blue  color  indicates  that  in  the  cook- 
ing of  starch  the  grains  are  broken  up  into  particles  sufficiently 
small  to  pass  readily  through  the  meshes  of  connnon  filter  paper. 

(4)  In  order  to  determine  whether  dilute  starch  paste  will,  in 
response  to  the  laws  of  osmosis,  pass  through  an  animal  membrane, 
fill  a  dialyzer  with  dilute  starch  paste.  Set  aside  to  be  tested  one 
or  two  days  later. 


158  SPECIAL  PHYSIOLOGY 

.(5)  Put  a  bit  of  absorbent  cotton  into  a  beaker  or  test-tube ;  add 
water;  boil;  add  iodine.  Cellulose  as  represented  by  cotton  fibres 
does  not  respond  to  the  iodine  test. 

(6)  Put  a  few  bits  of  ash-free  filter  paper  into  a  test-tube;  add 
water;  boil;  add  iodine.  Cellulose  as  represented  by  the  fibres  of 
ash-free  filter  paper  is  insoluble  in  water,  and  responds  to  the 
iodine  test.  One  must  remember  in  this  connection  that  in  the 
preparation  of  ash-free  filter  paper  mineral  acids  are  used  to  dis- 
solve out  the  salts;  and  mineral  acids,  especially  sulphuric  acid,  so 
modify  cellulose  that  it  responds  to  the  iodine  test  with  a  blue  color. 

(7)  Add  water  to  dextrine  in  a  beaker;  stir  with  a  rod.  Dextrine 
is  readily  soluble  in  cold  water.  To  a  small  portion  add  iodine. 
The  solution  will  probably  assume  a  wine  color;  the  typical  reaction 
of  erythrodextrine. 

(8)  Fill  a  dialyzer  with  diluted  dextrine  solution  and  leave  for 
subsequent  examination. 

(9)  Add  water  to  dextrose;  it  is  readily  soluble.  Add  iodine  to 
a  portion  of  the  solution;  result  negative. 

(10)  Fehling's  Test  for  a  Reducing  Sugar.  To  a  few  drops  of  the 
solution  add  several  cubic  centimetres  of  Fehling's  solution  and  boil. 
A  yellowish  precipitate  of  cuprous  oxide  (CuO)  appears.  If  the 
boiling  is  continued,  the  color  changes  to  a  brick-dust  red. 

(11)  To  a  solution  of  maltose  add  Fehling's  solution  and  boil; 
the  copper  solution  is  reduced  and  CuO  is  precipitated. 

(12)  To  a  solution  of  lactose  add  Fehling's  solution  and  boil; 
reduction  takes  place. 

(13)  Subject  a  solution  of  saccharose  to  the  Fehling  test.  No 
reduction  occurs.  Vary  the  test  by  boiling  the  solution  with  a  few 
drops  of  dilute  HCl  before  adding  the  Fehling  solution.  The  acid 
splits  the  disaccharid  cane-sugar  into  its  monosaccharid  components,, 
one  of  which  reduces  the  Fehling  solution. 

(14)  Trommer's  Test  for  a  Reducing  Sugar.  To  any  liquid  suspected 
of  containing  a  reducing  sugar,  add  a  few  drops  of  dilute  CuSO^ 
solution;  to  this  mixture  add  an  excess  of  NaOH  (or  KOH);  boil; 
if  the  suspected  liquid  contain  a  reducing  sugar  the  CuSO^  will  be 
reduced  with  precipitation  of  CuO.  Subject  all  of  the  solutions  of 
sugar  in  turn  to  the  Trommer  test.  Note  that  the  appearance  is  prac- 
tically the  same  as  with  the  Fehling  test.  Any  differences  are  due  only 
to  a  difference  in  the  proportions  of  the  two  reagents.  The  Fehling 
test  is  the  more  satisfactory  one. 

(15)  Fill  a  dialyzer  with  a  dilute  solution  of  dextrose  for  subsequent 
examination. 

(16)  Fill  a  dialyzer  with  a  dilute  solution  of  maltose  or  lactose  for 
subsequent  examination. 

(17)  Fill  a  dialyzer  with  a  dilute  solution  of  saccharose  for  subse- 
quent examination. 


DIGESTION  AND  ABSORPTION 


159 


Questions  and  Problems. 


Carbohydrates 


I.  Monasaccharids 


II.  Disaccharids 


Ig 


Dextrines 


Gums 


I.  III.  Polysaccharids     ■{ 


Starches 


{  Cellulose. 


Dextrose. 
Levulose. 
Galactose. 

Saccharose. 

Lactose. 

Maltose 

Erythrodextrine. 

AchroiJdextrine. 

Gum  arable. 

Vegetable. 

Animal:  glycogen. 


(a)  How  may  carbohydrates  be  classified?     (Make  three  classes.) 

(6)  Which  class  has  the  lowest  grade  of  hydration? 

(c)  How  many  of  this  class  are  soluble  in  cold  water? 

{d)  How  many  are  diffusible? 

(e)  Which  class  has  the  highest  grade  of  hydration? 

(/)  Are  all  of  those  which  belong  to  Classes  I.  and  H.  soluble  in 
water  ? 

ig)  Which  are  diffusible? 

(h)  How  many  of  the  carbohydrates  reduce  CuSO^  in  the  presence 
of  an  excess  of  NaOH  or  KOH? 

(i)  How  many  of  the  carbohydrates  are  diffusible? 

(;')  How  may  one  determine  whether  or  not  cane-sugar  passed 
through  the  animal  membrane? 


II.  SALIVARY  DIGESTION. 


1.  Materials.  Bread;  fibrin;  pig-fat;  olive  oil;  starch  paste; 
cane-sugar. 

2.  Preparation,  (a)  Remove  the  parotid  and  submaxillary  glands 
of  .several  rabbits  or  rats,  hash  them,  rinse  quickly  with  water  to 
remove  blood,  and  cover  with  water.  After  a  few  hours  (twelve  to 
twenty-four)  filter  or  strain  off  the  opalescent,  aqueous  extract.  It 
should  contain  an  aqueous  .solution  of  ptyalin.  Label:  Salivary 
Extract. 

(b)  Chew  a  piece  of  rubber  or  paraffin.  The  flow  of  .saliva  is 
.stimulated;  catch  the  .secretion  in  a  beaker;  dilute  and  filter.  Label: 
Salivari/  Secretion. 

(c)  Fibrin  for  u.se  in  experiments  on  digestion  may  l)e  procured 
in  any  quantity  at  a  .slaughter-liou.se.  Rid  it  of  all  red  coloring 
matter  and  of  accidental  contamination  by  repeatedly  .soaking  and 
washing  in  water.    The  white,  elastic  threads  of  fibrin  may  be  kept 


160  SPECIAL  PHYSIOLOGY 

indefinitely  in  pure  glycerin.     For  use  one  needs  only  to  wash  out 
the  glycerin  thoroughly. 

3.  Experiments  and  Observations.  (1)  Subject  saliva  (a)  and 
(6)  to  the  Fehling  test.  It  will  be  found  thaf  neither  the  extract 
nor  the  secretion  will  reduce  the  CuSO^. 

(2)  Subject  starch  paste  to  the  same  test.    The  result  is  negative. 

(3)  Mix  equal  volumes  of  starch  paste  and  salivary  extract  in  a 
beaker.  Place  the  mixture  in  the  incubator,  which  is  kept  at  a 
temperature  of  35°  to  40°  C.  After  ten  or  fifteen  minutes  subject 
the  mixture  to  a  test  with  Fehling' s  solution.  If  the  conditions  are 
normal  a  copious  precipitate  of  CuO  indicates  that  a  change  has 
been  wrought  in  the  mixture.  The  starch  has  been  changed  to  a 
reducing  sugar  by  the  ptyalin  of  the  salivary  extract. 

(4)  Mix  equal  volumes  of  starch  paste  and  salivary  secretion  in 
a  beaker;  place  the  mixture  in  the  incubator  for  ten  or  fifteen  minutes; 
test  with  Fehling's  solution.  The  presence  of  a  reducing  sugar 
shows  that  the  secretion  of  the  human  salivary  glands  has  the  power 
to  change  starch  to  sugar;  to  change  an  insoluble  diffusible  foodstuff 
to  a  soluble  diffusible  one. 

(5)  Put  a  few  crumbs  of  bread  in  a  test-tube;  add  dilute  iodine. 
Starch  is  an  important  constituent  of  bread. 

(6)  Put  a  few  crumbs  of  bread  in  a  beaker;  add  salivary  extract; 
place  in  the  incubator  twenty  minutes.  Disintegration  of  the  pieces 
and  a  marked  increase  of  the  amount  of  reducing  sugar  indicates 
the  digestive  action  of  saliva  upon  bread. 

(7)  Put  a  bit  of  fibrin  into  salivary  extract;  place  in  the  incubator. 
An  hour  or  a  day  will  show  no  apparent  change  in  the  fibrin.  Had 
one  used  any  other  proteid  the  result  would  have  been  the  same. 
We  are  justified  in  the  conclusion  that  saliva  contains  no  ferment 
capable  of  changing  proteids. 

{8)  Put  a  bit  of  fat  or  a  drop  of  oil  into  a  few  cubic  centimetres 
of  salivary  extract,  shake  vigorously;  place  in  incubator.  After  an 
hour  or  a  day  one  can  see  no  change  in  the  fat  or  oil,  and  is  justified 
in  the  conclusion  that  saliva  contains  no  ferment  which  acts  upon  fats. 

(9)  To  a  small  amount  of  raw  starch  add  salivary  extract;  place 
the  mixture  in  the  incubator;  shake  frequently;  after  fifteen  minutes 
test  for  reducing  sugar.  There  will  probably  be  a  relatively  small 
amount  of  reducing  sugar.  If  one  watches  the  progress  of  digestion 
for  several  hours  he  will  be  convinced  that  the  cooking  of  starch 
very  greatly  facilitates  its  digestion  by  saliva. 

(10)  Boil  a  few  cubic  centimetres  of  saliva;  add  starch  paste;  place 
in  the  incubator  for  ten  minutes;  test  for  reducing  sugar.  What  is 
the  verdict? 

(11)  Test  the  salivary  secretion  with  neutral  litmus.  Determine 
whether  its  faint  alkaline  reaction  is  essential  to  its  action  as  a 
digestive  fluid. 


DIGESTION  AND  ABSORPTION  161 

(a)  To  a  portion  of  saliva  add  an  equal  volume  of  0.3  per  cent, 
hydrochloric  acid  and  the  same  amount  of  starch  paste.  The  mix- 
ture represents  0.1  per  cent,  hydrochloric  acid.  Place  the  mixture 
in  the  incubator  for  fifteen  minutes;  test  with  Fehling's  solution. 
Verdict  ? 

(6)  Repeat  the  experiment,  substituting  for  the  hydrochloric  acid 
lactic  acid  of  the  same  strength;  place  in  the  incubator  for  fifteen 
minutes;  test  with  Fehling's  solution. 

What  is  the  conclusion? 

(12)  To  Determine  the  Course  of  Salivary  Digestion.  Mix  50  c.c. 
of  salivary  extract  with  an  equal  amount  of  starch  paste.  Test  a 
portion  with  iodine  at  once.  Test  another  portion  at  once  with 
Fehling's  solution.  Keep  the  beaker  in  a  water-bath  at  blood  temper- 
ature. Test  a  portion  of  the  mixture  every  minute  with  iodine  and 
another  portion  every  minute  with  Fehling's  solution. 

(a)  What  is  the  first  change  noted  in  the  digestion  of  the  starch  ? 
(6)  How  many  steps  may  be  made  out  with  the  means  used  and 
under  the  conditions  existing  in  the  experiment? 
(c)  In  what  order  do  the  changes  occur? 

(13)  Place  some  starch  paste  in  a  beaker  which  may  be  floated 
in  ice-water;  similarly  float  a  beaker  with  saliva.  After  both  liquids 
have  been  cooled  down  to  near  the  temperature  of  the  surrounding 
water,  mix  them  in  one  of  the  beakers,  keep  the  mixture  at  the 
low  temperature  while  subjecting  portions  of  it  every  two  minutes 
to  the  tests  suggested  above. 

(a)  May  the  same  changes  be  made  out  in  this  experiment  as  in 
the  previous  one? 

(b)  Are  the  changes  in  the  same  order? 

(c)  State  any  differences  in  salivary  digestion  at  blood  temperature 
and  at  low  temperature  (0°  C.)  used  in  this  experiment. 

(14)  (a)  Sum  up  the  day's  work  in  a  series  of  conclusions. 

(6)  What  is  the  chemical  formula  of  starch?  Of  erythrodextrine? 
Of  maltose?     Of  dextrose? 

(c)  Write  a  chemical  reaction  or  a  series  of  reactions  which  will 
be  in  harmony  with  the  observations  and  show  as  nearly  as  possible 
the  course  of  salivary  digestion. 

(d)  What  change  has  the  ferment  wrought  in  the  starch  molecule 
to  render  the  resulting  carbohydrate  capable  of  diffusion  through 
animal  membrane? 


III.  THE  PROTEIDS. 

1.  Materials.  An  egg;  fibrin;  gelatin;  myosin;  syntonin;  acid 
albumin;  commercial  peptone  (mixed  albumoses,  proteoses,  and 
peptones);  Griibler's  pure  peptone. 

11 


162  SPECIAL  PHYSIOLOGY 

2.  Preparation,  (a)  To  Prepare  Myosin.  (1)  Take  one  pound 
of  lean  meat,  grind  it  in  the  meat  hasher;  soak  and  wash  repeatedly 
until  the  tissue  is  nearly  white  and  quite  free  from  haemoglobin. 

(2)  Put  the  washed  muscle  tissue  into  a  flask  with  an  equal  bulk 
of  a  20  per  cent,  solution  of  ammonium  chloride;  shake  from  time 
to  time  for  twenty-four  hours. 

(3)  Strain  off  the  liquor  and  add  it  to  twenty  volumes  of  distilled 
water.  Myosin  is  precipitated.  Wash  the  precipitate,  redissolve 
one-fourth  of  the  precipitate  in  10  per  cent.  NaCl  and  label:  Saline 
Solution  of  Myosin. 

(b)  To  Prepare  Syntonin.  To  the  remaining  three-fourths  of  the 
washed  myosin  add  several  volumes  of  0.1  per  cent,  hydrochloric 
acid.  In  a  very  short  time  the  myosin  will  be  dissolved  and  changed 
to  syntonin. 

(c)  To  Prepare  Dilute  Egg  Albumin.  Make  an  opening  in  end  of 
the  shell  of  an  egg;  drain  off  the  white  of  the  egg,  catching  it  upon  a 
coarse  linen  cloth — a  towel  serves  the  purpose  well;  press  the  albumin 
through  the  meshes  of  the  linen  into  a  beaker;  add  400  or  500  c.c.  of 
distilled  water;  transfer  the  mixture  to  a  1-litre  cylinder,  and  shake 
vigorously;  after  a  short  time  filter  through  pure  absorbent  cotton  or 
strain  through  fine  linen. 

(d)  To  Prepare  Acid  Albumin.  To  100  c.c.  of  dilute  egg  albumin 
add  an  equal  quantity  of  0.2  per  cent,  hydrochloric  acid;  place  the 
mixture  in  the  incubator  for  two  or  three  hours.  Though  the  change 
begins  at  once,  it  will  probably  not  be  complete  before  the  time  sug- 
gested. If  one  wishes  to  isolate  the  acid  albumin  from  the  mixture, 
he  has  only  to  carefully  neutralize  with  sodic  hydroxide,  precipitating 
the  acid  albumin,  and  to  wash  the  precipitate  with  distilled  water. 
For  the  purposes  for  which  it  is  to  be  used  in  the  following  demon- 
stration, it  may  be  left  in  the  acid  solution,  which  represents  0.1  per 
cent.  HCl.    Label:  Acid  Albumin  Solution  in  0.1  per  cent.  HCl. 

(e)  Make  an  aqueous  solution  of  the  commercial  "peptone,"  and, 
though  the  peptone  is  present  in  small  proportions,  label  it  Pi'o- 
teoses. 

(/)  Make  an  aqueous  solution  of  a  few  grams  of  Griibler's  pure 
peptone  and  label:  Peptone. 

(g)  Dissolve  a  few  grams  of  gelatin  in  distilled  water. 

(h)  To  Prepare  Millon's  Reagent.  1.  To  100  grams  of  pure  mer- 
cury add  an  equal  weight  of  concentrated  nitric  acid,  c.  p.  The  reac- 
tion proceeds  at  room  temperature,  though  gentle  heat  may  be  applied 
to  complete  the  solution  of  the  mercury.  2.  Cool  the  mixture;  add 
two  volumes  of  water;  after  twelve  hours  decant  the  supernatant 
liquid — Millon's  Reagent. 

3.  Experiments  and  Observations.  (1)  The  Heat  Test.  Pour 
into  test-tubes  a  few  cubic  centimetres  of  each  of  the  following  pro- 
teid  solutions  and  subject  each  in  turn  to  a  temperature  of  63°  C,  and, 


DIGESTION  AND  ABSORPTION  163 

finally  to  a  temperature  of  100°  C,  by  dipping  the  tubes  into  water- 
baths  of  the  temperatures  named: 

(a)  Dilute  egg  albumin. 

(6)  Saline  solution  of  myosin. 

(c)  Syntonin  in  acid  solution. 

{d)  Acid  albumin  in  acid  solution. 

{e)  Gelatin  in  aqueous  solution. 

(/)  Proteoses. 

ig)  Peptone. 

Record  results  in  a  table  and  formulate  conclusions. 

(2)  The  Cold  Nitric  Acid  Test.  Subject  the  same  series  of  proteids 
to  the  cold  nitric  acid  test  by  first  pouring  1  c.c.  or  2  c.c.  of  strong 
nitric  acid  into  a  test-tube;  then,  with  pipette,  carefully  floating 
the  proteid  licjuid  upon  it.  In  the  case  of  the  dilute  egg  albumin, 
a  characteristic  white  ring  forms  between  the  acid  and  the  albumin. 
Note  in  each  case  whether  or  not  a  typical  ring  is  formed. 

(a)  Dilute  egg  albumin. 

(6)  Saline  solution  of  myosin. 

(c)  Syntonin. 

{d)  Acid  albumin. 

{e)  Gelatin. 

(/)  Proteoses. 

(g)  Peptone. 

Tabulate  results  and  formulate  conclusions  in  a  concise  statement. 

(3)  The  Xanthoproteic  Test.  Use  the  tubes  and  materials  already 
prepared  in  the  cold  nitric  acid  test.  Shake  the  tubes  to  mix  the 
acid  with  the  proteid.  In  some  cases  a  coagulum  will  be  formed,  and 
this  coagulum  turns  yellow  on  boiling  if  the  tube  is  held  in  a  Bunsen 
flame.  After  the  coagulum  has  been  boiled  in  the  acid,  cool  under 
the  hydrant  or  in  a  pail  of  ice- water  and  add  strong  ammonia  to 
alkaline  reaction.  The  light-vellow  coagulum  which  forms  in  the 
case  of  the  egg  albumin  turns  to  an  orange  color.  This  test  is  usually 
given  as  a  universal  proteid  test.  Tabulate  results  on  the  above 
suggesterl  series  (a)  to  {g),  noting  any  variations  of  the  reaction  with 
different  proteids.  Note  variations  in  the  reaction  with  different 
strengths  of  solution  of  the  same  proteid. 

(4j  Millon's  Test.  A  general  test  for  proteids  is  to  heat  a  proteid- 
containing  liquid  with  half  its  volume  of  Millon's  reagent.  A  pre- 
cipitate appears,  which  is  yellowish  at  first,  but  turns  red  under  the 
influence  of  heat.  Test  each  of  the  above  list  of  proteids  (a)  to  (g) 
with  Millon's  reagent.     Record  results. 

(h)  The  Biuret  Test.  To  a  suspected  lifjuid  add  an  excess  of  sodic 
hydrate;  shake  well,  and  to  the  mixture  add  one  or  two  drops  of  a 
very  dilute  solution  of  cupric  sulphate.  A  violet  color  appears,  which, 
on  heating,  becomes  deeper  in  shade. 

A  most  convenient  reagent  for  this  reaction  is  a  mixture  of  the 


164  SPECIAL  PHYSIOLOGY 

solutions  (a)  and  (h)  of  the  Fehling  solution,  but  in  the  proportion  of 
nine  parts  of  the  sodic  hydroxide  solution  (h)  to  one  part  of  the  cupric 
sulphate  solution  {a),  and  add  an  equal  volume  of  the  distilled  water 
to  the  mixture. 

Tabulate  results  on  the  proteid  series  (a)  to  {g). 

(6)  Subject  each  of  the  series  of  proteids  (a)  to  {g)  to  each  of  the 
following  reagents,  tabulating  results: 

(I)  Picric  acid,  saturated  solution. 
(II)  Absolute  alcohol. 

(III)  Mercuric  chloride,  saturated  solution. 

(IV)  Tannic  acid,  saturated  solution. 
(V)  Silver  nitrate,  10  per  cent,  solution. 

(VI)  Ammonium  sulphate,  saturated  solution. 
On  which  of  the  proteid  solutions  would  one  get  a  precipitate  with 
silver  nitrate  independent  of  the  presence  of  proteid? 

(7)  To  Separate  Peptone  from  Other  Proteids.  It  will  have  been  noted 
that  ammonium  sulphate  precipitates  all  proteids  except  pure  pep- 
tone. If  one  has  peptone  mixed  with  proteoses  and  unchanged  pro- 
teids, one  may  demonstrate  its  presence  by  precipitating  out  the 
other  proteids  and  then  demonstrating  by  such  a  test  as  the  Biuret 
test  the  presence  of  a  proteid  in  the  clear  filtrate;  that  could  be 
nothing  else  than  peptone. 

Test  commercial  peptone  in  this  way  and  determine  whether  any 
appreciable  proportion  of  it  is  peptone. 

(8)  The  Diffusibility  of  Proteids.  Fill  seven  dialyzers  with  proteids 
above  studied.    On  the  following  day  test  the  diffusates  for  proteids. 

IV.   (a)  DIFFUSIBILITY  OF  PROTEIDS.     (b)  MILK. 
(a)  Diffusibility  of  Proteids. 

1.  Materials.  The  seven  dialyzers  filled  at  the  end  of  the  pre- 
vious demonstration. 

2.  Experiments  and  Observations.  (1)  What  reagent  may  best 
be  used  to  determine  whether  or  not  any  of  the  egg  albumin  has 
diffused  through  the  animal  membrane? 

(2)  How  may  one  determine  whether  or  not  any  of  the  salts  of  the 
egg  albumin  have  diffused  through  the  membrane? 

(3)  In  the  case  of  the  saline  solution  of  myosin  (h),  of  syntonin  (c), 
and  of  acid  albumin  {d),  is  there  any  contraindication  against  silver 
nitrate  as  a  reagent  to  determine  whether  proteid  has  diffused? 

(4)  What  tests  would  be  most  reliable  in  these  cases  to  detect  the 
presence  of  proteid  in  the  diffusate? 

(5)  Would  a  trace  of  proteid  in  the  diffusate  necessarily  demon- 
strate the  diffusibility  of  these  proteids  through  the  walls  of  the 
alimentary  tract?    If  not,  why  not? 


DIGESTION  AND  ABSORPTION  165 

(6)  "What  tests  may  be  used  to  determine  the  presence  of  gelatin 
in  the  diffusate?     Is  gelatin  diffusible? 

(7)  The  term  proteoses  is  a  general  one  and  is  used  to  designate 
the  mid-products  of  proteid  digestion.  The  mid-product  of  albumin 
digestion  is  albumose;  of  globulin  digestion,  globulose;  of  myosin, 
myosinose;  of  vitellin,  vitellinose;  of  casein,  caseinose;  or,  in  general, 
of  a  proteid,  proteose. 

Dialyzer  (/)  contains  products  of  peptic  digestion  of  proteids, 
principally  albumin.  The  progress  of  digestion  was  suspended  at  a 
stage  where  there  were  present  not  only  peptone,  but  mid-products — 
albumoses;  or,  to  use  the  general  term,  proteoses. 

The  problem  which  confronts  us  is  to  determine  whether  or  not 
proteoses  are  diffusible. 

(a)  If  peptone  is  diffusible,  the  diffusate  will  certainly  contain  pep- 
tone. Do  peptone  and  proteoses  respond  alike  to  all  the  general  tests 
for  proteoses? 

(6)  How  may  peptone  be  separated  from  the  proteoses?  What 
single  reagent  is  indicated  in  the  case? 

(8)  Demonstrate  the  diffusibility  of  peptone. 

(b)  Milk. 

1.  Materials.  One  litre  of  fresh  whole  milk;  one  litre  of  milk  for 
the  preparatory  steps  of  the  demonstration. 

2.  Preparation.  (1)  On  the  day  before  the  demonstration  fill  a 
500-c.c.  open-mouthed  cylinder  with  milk  and  put  it  in  a  cool  place. 

(2)  Two  days  before  the  demonstration  weigh  out  10  grams  to  50 
grams  of  whole  milk  in  a  platinum  dish  or  in  a  thin  porcelain  dish. 
Place  it  in  a  drying  oven  at  90°  to  95°  C,  and  dry  to  constant 
weight.    Record  the  dry  weight. 

(3)  Before  the  hour  of  demonstration  burn  the  residue  by  bringing 
the  dish  which  contains  the  dry  solids  to  a  red  glow  in  a  Bunsen 
flame,  allowing  ample  access  of  oxygen.  After  the  dish  and  the  white 
ashes  have  cooled  in  a  desiccator,  take  the  weight.  All  of  these 
weights  should,  of  course,  be  taken  upon  an  analytical  balance. 

(4)  Fill  a  dialyzer  with  diluted  milk  one  day  before  the  demon- 
stration. 

.J.  Experiments  and  Observations.  (1)  What  proportion  of  milk 
evaporates  at  the  temperature  above  suggested?  It  may  be  taken 
for  granted  that  this  proportion  represents  practically  the  water  of 
the  milk. 

(2)  Oi  the  solids  of  milk,  what  proportion  is  organic  and  what 
proportion  is  inorganic? 

(3)  What  bases  predominate  in  the  ashes? 

(4)  What  is  the  character  of  the  organic  constituents  of  milk? 
(a)  Note  that  the  milk  that  has  been  standing  has  separated  into 


166  SPECIAL  PE YSIOL OGY 

two    layers,   an  upper    yellowish  layer  and    a    lower    bluish-white 
layer. 

(b)  Draw  oflP  with  pipette  a  few  cubic  centimetres  of  the  cream  and 
in  a  test-tube  add  an  equal  volume  of  osmic  acid.  To  a  few  drops  of 
olive  oil  in  another  tube  add  osmic  acid.  Shake  both  tubes  vigor- 
ously. Osmic  acid  has  the  same  effect  upon  cream  as  upon  olive  oil. 
The  cream  is,  in  fact,  fat  in  physiological  emulsion.  Quantitative 
examination  shows  that  about  4  per  cent,  of  milk,  or  ^  of  the  solids 
of  milk,  consists  of  fats  in  which  olein  predominates. 

(5)  Fill  a  siphon  with  water  and  introduce  it  through  the  cream  to 
the  bottom  of  the  500-c.c.  cylinder;  draw  off  300  c.c.  of  the  milk; 
add  to  it  four  volumes  of  water;  slowly  add  1  per  cent,  acetic  acid, 
while  stirring  with  a  rod,  until  the  casein  separates  as  a  copious 
flocculent  precipitate.  After  the  casein  has  partially  settled,  decant 
off  a  few  cubic  centimetres  of  the  supernatant  liquid  and  subject  it 
to  the  Fehling  test.  The  abundant  precipitate  indicated  the  pres- 
ence of  a  reducing  sugar.    It  is  milk-sugar — lactose. 

(6)  Wash  the  casein  by  the  repeated  addition  of  water,  followed 
by  decantation;  pour  it  into  a  linen  sack  or  a  towel  and  press  out  the 
water;  further  extract  the  water  with  absolute  alcohol;  extract  the 
remnant  of  fat  with  ether;  dry  in  the  air.  The  white  granular  material 
that  remains  is  nearly  pure  casein,  the  most  important  proteid  of  milk, 
and  represents  nearly  4  per  cent,  of  milk. 

(7)  Heat  100  c.c.  of  the  fresh  milk  in  a  beaker.  Before  the  boiling 
point  is  reached  a  membrane  gathers  upon  the  surface  of  the  milk. 
This  membrane  represents  the  lactalhumin  of  the  milk,  which  has 
been  coagulated  by  the  heat  and  has  collected  in  the  membranous 
coagulum  at  the  surface.  The  lactalbumin  represents  only  a  small 
proportion  of  the  milk  proteid.  Subject  the  membrane  to  the  xantho- 
proteic test  or  the  Millon  test  to  demonstrate  that  it  is  a  proteid. 

(8)  To  30  c.c.  of  fresh  milk  in  a  beaker  add  common  salt  to  satura- 
tion.    Record  results. 

(9)  To  30  c.c.  of  fresh  milk  in  a  beaker  add  magnesium  sulphate 
to  saturation.     Record  results. 

(10)  Dilute  fresh  milk  to  one-fifth  normal  and  subject  it  to  the 
following  tests,  recording  results: 

(a)  Trommer's  test. 

(b)  The  xanthoproteic  test. 

(c)  The  biuret  test. 

{d)  The  osmic  acid  test. 

(11)  Fill  a  dialyzer  with  the  diluted  milk.  One  day  later  examine 
the^diffusate: 

(a)  For  any  of  the  inorganic  constituents  of  milk. 
(6)  For  the  carbohydrate  constituents  of  milk. 
(c)  For  the  proteid  constituents  of  milk. 
{d)  For  the  fatty  constituents  of  milk. 


DIGESTION  AND  ABSORPTION  167 

(12)  Formulate  in  a  series  of  concise  statements  the  facts  demon- 
strated regarding  milk: 

(a)  Its  chemical  constituents. 
(6)  Its  physical  properties. 


V.  GASTRIC  DIGESTION. 

1.  Materials.  Two  fresh  pig-stomachs;  h  kilo  clean  sea-sand; 
four  eggs;  fibrin;  bread;  milk;  jellied  gelatin;  casein,  and  rennin. 

2.  Preparation.  (1)  To  Prepare  Artificial  Gastric  Juice,  (a)  Stretch 
a  fresh  stomach  of  a  pig  upon  a  board,  with  mucous  surface  up; 
fasten  in  place  with  nails. 

(6)  Rinse  off  the  mucous  membrane  gently  with  cold  water. 

(c)  Scrape  thoroughly  with  a  dull-edged  table  knife  or  an  equiva- 
lent; collect  the  scrapings  in  a  large  mortar. 

{d)  Grind  the  scrapings  in  clean,  fine  sand. 

(e)  Add  an  equal  volume  of  0.2  per  cent.  HCl  and  leave  for  twenty- 
four  to  forty-eight  hours,  stirring  occasionally. 

(/)  Strain  through  linen;  filter,  and  preserve  in  a  glass-stoppered 
bottle.     Label:  Acidulated  Aqueous  Extract  of  Pepsin. 

(g)  For  use  dilute  this  extract  with  three  or  four  volumes  of  0.1  per 
cent.  HCl.     Label:  Artificial  Gastric  Juice  (1). 

(2)  To  Prepare  a  Glycerin  Extract  of  Pepsin,  (a)  Rinse  off  the 
mucous  membrane  of  a  fresh  pig  stomach  with  cold  water  and 
remove  the  mucous  membrane  from  the  muscular  walls  of  the 
stomach. 

(6)  Grind  the  mucous  membrane  in  the  meat  hasher. 

(c)  Put  the  hashed  tissue  into  a  beaker  and  cover  with  two  volumes 
of  pure  glycerin.  Stir  the  mixture  occasionally  for  several  days.  The 
glycerin  extracts  the  pepsin  ferment. 

(d)  Strain  the  glycerin  extract  through  fine  linen;  preserve  in  a 
glass-stoppered  bottle  for  future  use.    It  will  keep  indefinitely. 

(e)  For  use  add  to  one  volume  of  the  extract  thirty  to  fifty  volumes 
of  0.2  per  cent.  HCl.     Label:  Artificial  Gastric  Juice  (2). 

3.  Experiments  and  Observations.  (1)  To  a  bit  of  starch 
paste  of  the  consistency  of  jelly  add  artificial  gastric  juice  (1);  place 
in  the  incubator;  in  ten  minutes  or  one  day  note  results. 

(2)  To  a  few  drops  of  olive  oil  or  to  a  bit  of  pure  tallow  add  several 
cubic  centimetres  of  gastric  juice  and  keep  at  incubator  temperature 
for  one  day.    What  effect  has  gastric  digestion  upon  fat  or  oil? 

C-i)  To  a  bit  of  pig-fat  add  gastric  juice  and  keej)  at  incubator  tem- 
perature for  .several  hours.  What  effect  has  gastric  digestion  upon 
adipo.se  tissue? 

(4)  To  a  bit  of  fibrin  in  a  test-tube  add  gastric  juice.  The  warmth 
of  the  hand  will  be  sufficient.     If  the  preparation  of  artificial  gastric 


168  SPECIAL  PHYSIOLOGY 

juice  has  been  successful  the  fibrin  will  dissolve  in  one  or  two  minutes. 
One  may  be  certain  that  digestion  is  progressing  rapidly,  though 
complete  solution  of  the  fibrin  does  not  necessarily  indicate  complete 
digestion  of  it;  for  complete  digestion  of  a  proteid  implies  that  the 
foodstuff  is  both  dissolved  and  diffusible.  The  fibrin  is  dissolved; 
it  may  or  may  not  be  diffusible.    But  this  will  be  determined  later. 

(5)  To  Determine  the  Active  Factors  of  Gastric  Digestion,  (a)  To 
a  few  shreds  of  fibrin  in  a  test-tube  add  a  few  cubic  centimetres  of 
0.2  per  cent.  HCl.  Carefully  note  results.  Will  dilute  HCl  dissolve 
fibrin?    Is  it  possible  to  digest  a  proteid  without  dissolving  it? 

(6)  To  fibrin  add  dilute  neutral  glycerin  extract  of  pepsin.  Is 
solution  effected? 

(c)  To  tube  (a)  add  a  few  drops  of  the  glycerin  extract  of  pepsin. 

(d)  To  tube  (6)  add  two  volumes  of  0.2  per  cent.  HCl.  Note 
results.     Formulate  conclusions. 

(6)  To  Determine  whether  the  Acid  Factor  of  Gastric  Digestion 
Need  Necessarily  Be  Hydrochloric  Acid.  Prepare  a  0.4  per  cent, 
solution  of  each  of  the  following  acids: 

(I)  Lactic  acid. 

(II)  Sulphuric  acid. 

(III)  Nitric  acid. 

(IV)  Phosphoric  acid. 
(V)  Citric  acid. 

(VI)  Acetic  acid. 
(VII)  Malic  acid. 
For  each  acid  prepare  four  test-tubes  as  follows: 

(a)  Fibrin+1  c.c.  glyc.  ext.  of  pepsin+10  c.c.  0.4  per  cent.  acid. 

(b)  Fibrin +  1  c.c.  pepsin  ext. +  10  c.c.  0.2  per  cent.  acid. 

(c)  Fibrin  +  1  c.c.  pepsin  ext. +  10  c.c.  0.1  per  cent.  acid. 

(d)  Fibrin+1  c.c.  pepsin  ext. +  10  c.c.  0.05  per  cent. 
Proceed  in  a  similar  manner  with  each  acid. 

Tabulate  results.  May  other  acid  or  acids  take  the  place  of 
HCl  as  a  factor  in  digestion?  If  so,  in  what  minimum  strength? 
Which  one  of  the  above  acids  is  normally  present  in  the  stomach? 
May  any  of  the  above  acids  serve  as  digestives  and  as  foods? 

As  digestives  and  as  tonics? 

As  digestives,  foods,  and  tonics? 

Cite  authorities. 

(7)  To  Determine  the  Optimum  Strength  of  the  Hydrochloric  Acid. 
Prepare  with  care  the  following  three  dilutions  of  hydrochloric  acid: 
10  per  cent.,  1  per  cent.,  0.1  per  cent. 

Into  twelve  test-tubes  put  as  many  small  masses  of  fibrin;  into 
each  tube  put  1  c.c.  of  neutral  10  per  cent,  dilution  of  glycerin  extract 
of  pepsin.    Label  and  fill  the  tubes  as  follows: 

Tube  (a)  5  per  cent.:  Add  to  the  fibrin  5  c.c.  of  10  per  cent. 
HCl  and  of  distilled  water  a  quantity  sufficient  to  make  10  c.c. 


DIGESTIOX  AND  ABSORPTION  169 

Tube  (6)  2  per  cent.:  Add  2  c.c.  of  10  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  (c)  1  per  cent.:  Add  1  c.c.  of  10  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  {d)  0.5  per  cent.:  Add  5  c.c.  of  1  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  {e)  0.4  per  cent.:  Add  4  c.c.  of  1  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  (/)  0.3  per  cent.:  Add  3  c.c.  of  1  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  {g)  0.2  per  cent.:  Add  2  c.c.  of  1  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  (h)  0.1  per  cent.:  Add  1  c.c.  of  1  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  ij)  0.05  per  cent.:  Add  5  c.c.  of  0.1  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  (k)  0.025  per  cent.:  Add  2.5  c.c.  of  0.1  per  cent.  HCl  and 
aqua  dest.  cj.  s.  ad  10  c.c. 

Tube  (/)  0.01  per  cent.:  Add  1  c.c.  of  0.1  per  cent.  HCl  and  aqua 
dest.  q.  s.  ad  10  c.c. 

Tube  im)  0.005  per  cent.:  Add  1.2  c.c.  of  0.1  per  cent.  HCl  and 
aqua  dest.  q.  s.  ad  10  c.c. 

Place  these  twelve  tubes  in  the  incubator  and  note  conditions 
every  ten  minutes  for  the  first  hour,  every  hour  for  the  first  six  hours,, 
and  then  at  the  end  of  one  or  two  days  make  the  final  observations. 

Tabulate  results.  Formulate  conclusions.  What  range  of  strength 
may,  from  the  experiments  with  the  artificial  gastric  juice  under 
artificial  conditions,  be  considered  the  optimum  strength  for  the  acid  ? 
Is  there  any  reason  to  doubt  that  the  optimum  strength  as  determined 
above  is  essentially  different  from  the  optimum  strength  in  normal 
digestion  ? 

CS)  To  Determine  How  Dilute  the  Pepsin  May  Be  and  Still  Be 
EflBcient  in  Digestion.  This  experiment  requires  a  standard  solution 
of  pepsin  to  use  as  a  basis.  The  U .  S.  Pharmacopoeia  (p.  295  of  the 
7th  Decennial  Revision)  gives  the  following  formula  for  a  standard 
solution  of  pepsin: 

Hydrochloric  acid  (absolute),  0.21  grm. 

Pepsin  (pure),  0.00335  grm. 

Water  (distilled),  q.  s.  ad  100  c.c. 

The  following  suggestions  are  made  as  to  method  of  preparation: 
To  294  c.c.  of  water  adrl  6  c.c.  of  dilute  hydrochloric  acid — sol.  A. 
In  100  c.c.  of  sol.  A  dissolve  0.007  grm.  of  standard  pepsin — sol. 
B.  To  295  c.c.  of  sol.  A  at  40°  C.  add  5  c.c.  sol.  B.  The  resulting 
mixture  is  a  .standard  artificial  gastric  juice  of  the  formula  given 
above,  and  has  the  power  of  completely  digesting  at  3S°  to  40°  C. 
one-fifth  its  weight  of  coagulated  egg  albumin  in  six  hours. 


170  SPECIAL  PHYSIOLOGY 

From  a  standard  gastric  juice  prepare  the  following  dilutions, 
using  0.1  per  cent.  HCl  as  a  diluent.  It  is  scarcely  necessary  to  say 
that  the  greatest  care  should  be  taken  (1)  to  make  all  measurements 
with  precision,  and  (2)  to  thoroughly  shake  each  dilution  before 
drawing  off  material  for  the  next  lower  dilution. 

(a)  Standard  artificial  gastric  juice  10  c.c.  +  l  c.c.  moist  fibrin. 

(6)  1 :  10  standard  artificial  gastric  juice  10  c.c.  + 1  c.c.  moist  fibrin. 

(c)  1:100  standard  artificial  gastric  juice  10  c.c.  +  l  c.c.  moist 
fibrin. 

{d)  1:1000  standard  artificial  gastric  juice  10  c.c.  +  l  c.c.  moist 
fibrin. 

(e)  1:10,000  standard  artificial  gastric  juice  10  c.c.  +  l  c.c.  moist 
fibrin. 

(/)  1 :  100,000  standard  artificial  gastric  juice  10  c.c.  +  l  c.c.  moist 
fibrin. 

{g)  1:1,000,000  standard  artificial  gastric  juice  10  c.c.  +  l  c.c. 
moist  fibrin. 

Keep  tubes  in  incubator  or  water-bath  at  38°  to  40°  C.  Note 
(1)  time  required  to  dissolve  fibrin  completely;  (2)  time  required  to 
change  all  acid  albumin  to  proteose  or  peptone.  Will  one-millionth 
standard  gastric  juice  digest  fibrin  at  all?  Will  a  lower  dilution 
(one-ten-millionth)  digest  it?  If  so,  how  dilute,  and  how  long  a 
time  required? 

VI.  GASTRIC  DIGESTION  (Continued). 

Experiments  and  Observations  {Continued).  (9)  To  Determine 
the  Influence  of  the  Hydrochloric  Acid  of  the  Gastric  Juice  upon 
Putrefaction  in  the  Stomach.  ,  It  has  been  determined  that  the  hydro- 
chloric acid  in  the  stomach  destroys,  under  favorable  conditions,  at 
least  the  non-pathogenic  forms  of  bacteria.  Let  us  determine  the 
strength  of  acid  necessary  to  destroy  the  common  bacteria  of  putre- 
faction. To  each  tube  used  in  experiment  (7)  add  a  minute  drop 
of  any  putrefying  fluid.  If  the  contents  of  a  tube  serve  as  a  good 
culture  field,  any  drop  of  the  fluid  may  be  found  to  be  swarming 
with  bacteria  within  a  few  hours.  Within  a  few  hours  after  infecting 
the  tubes  examine  under  high  power — 700  to  1000  diameters — a  drop 
of  the  contents  of  each  tube.  While  making  the  observations  take 
care  not  to  contaminate  one  tube  with  the  contents  of  another.  That 
the  tubes  containing  5  per  cent,  or  2  per  cent,  or  1  per  cent,  hydro- 
chloric acid  will  be  found  to  be  free  from  bacteria  goes  without 
saying.  Just  how  weak  may  the  acid  be  and  destroy  the  bacteria? 
How  weak  may  the  acid  be  and  retard  their  development?  Could 
one  readily  drink  enough  liquid  at  a  meal  to  change  the  stomach 
from  a  sterilizing  field  to  a  culture  field  for  the  bacteria  of  putre- 
faction ? 


DIGESTION  AND  ABSORPTION  ]71 

(10)  The  Influence  of  Division  upon  the  Time  Required  to  Digest 
Proteids.  Boil  an  egg  five  to  ten  minutes;  cool  quickly;  separate  hard, 
coagulated  white  from  yolk  and  envelopes. 

(a)  Cut  out  one-centimetre  cube  and  put  it  into  a  beaker  with 
40  c.c.  artificial  gastric  juice. 

(6)  Put  into  a  second  beaker'of  40  c.c.  gastric  juice  a  centimetre 
cube  which  has  been  divided  into  eight  half-centimetre  cubes. 

(c)  Prepare  another  beaker  in  which  are  sixteen  quarter-centimetre 
cubes  in  10  c.c.  of  artificial  gastric  juice. 

{d)  Into  another  beaker  with  10  c.c.  of  artificial  gastric  juice  put 
one-quarter  of  a  cubic  centimetre  of  the  egg  albumin  which  has 
been  finely  divided  by  pressing  through  a  fine  sieve. 

Note  time  required  in  each  case  to  completely  digest  the  albumin. 

Has  this  any  hygienic  bearing? 

(11)  The  Influence  of  Temperature  upon  the  Time  Required  to 
Digest  Proteids.  Prepare  five  tubes  by  first  providing  each  with 
5  c.c.  of  artificial  gastric  juice;  treat  the  several  tubes  as  follows: 

(a)  Bring  to  40°  C.  in  water-bath;  add  fibrin;  note  time. 

(b)  Bring  to  30°  C.  in  water-bath;  add  fibrin;  note  time. 

(c)  Bring  to  20°  C.  in  incubator;  add  fibrin;  note  time. 
{d)  Leave  at  room  temperature  (10°  C);  note  time. 

(e)  Bring  to  0°  C.  in  ice-water;  add  fibrin;  note  time. 

What  is  the  optimum  temperature? 

Is  the  progress  of  digestion  materially  retarded  by  a  reduction  of 
the  temperature? 

Would  the  temperature  of  the  stomach  contents  be  essentially 
lowered  by  the  occasional  sipping  of  an  iced  beverage  during  a  meal? 

What  is  the  hygienic  significance  of  the  experiment? 


VII.  GASTRIC  DIGESTION  (Continued). 

Experiments  and  Observations  {Continued).  (12)  The  Steps  of 
Gastric  Digestion.  Boil  an  egg  five  to  ten  minutes;  cool  quickly; 
separate  out  the  white;  press  it  through  a  fine  sieve;  put  into  a 
beaker  with  100  c.c.  artificial  gastric  juice,  and  place  the  beaker 
in  a  water-bath  at  40°  C.  At  intervals  of  two  minutes  for  the  first 
ten  minutes,  then  at  intervals  of  five  minutes  for  the  next  twenty 
minutes,  then  at  intervals  of  ten  minutes  for  the  second  half-hour, 
afterward  at  intervals  of  one  hour,  subject  the  liquid  to  tests  for 
egg  albumin,  for  acid  albumin,  for  all)iimose,  for  peptone.  In  what 
order  and  after  what  length  of  time  do  the  several  products  appear? 
Is  the  one  that  is  first  to  appear  also  first  to  disappear? 

(13j  The  Artificial  Digestion  of  Various  Proteids.  (a)  To  a  small 
mass  of  jellied  gelatin  add  ten  to  fifteen  volunu's  of  artificial  gastric 
juice  and  note  effect. 


172  SPEC  I  A  L  PH  YSIOL  OGY 

(b)  Subject  bread  to  the  xanthoproteic  test.  The  presence  of 
proteid  material  is  demonstrated.  Put  a  small  piece  of  dry  bread 
into  a  beaker  with  gastric  juice  and  note  effect. 

(c)  Note  the  course  of  casein  digestion. 

(d)  Triturate  in  a  mortar  well-cooked  lean  meat;  digest  with 
gastric  juice. 

(e)  Try  the  xanthoproteic  test  upon  cooked  beans  or  peas;  proteid 
is  present.    Triturate  in  a  mortar;  digest. 

(/)  In  each  case  demonstrate  the  ultimate  appearance  of  peptone. 

(14)  The  Artificial  Digestion  of  Milk.  Of  fresh  milk  take  three 
portions  of  5  c.c.  each. 

(a)  To  one  portion  add  ten  volumes  of  artificial  gastric  juice  and 
place  it  in  the  incubator  at  38°  to  40°  C. 

(b)  Prepare  another  beaker  in  the  same  way,  but  place  it  in  a 
water-bath  at  38°  to  40°  C.  and  keep  the  mixture  well  stirred,  divid- 
ing the  casein  coagulum  as  fine  as  possible. 

(c)  Place  the  third  portion  of  milk  in  the  water  bath.  When  it 
has  become  warm  add  a  few  centimetres  of  rennin.  Fifteen  minutes 
later  add  artificial  gastric  juice.  Stir  as  in  (6).  In  which  of  the  first 
two  does  digestion  seem  to  progress  the  more  rapidly?  Does  the 
progress  or  process  of  the  digestion  seem  to  be  materially  different 
in  the  last  two  experiments  (6)  and  (c)  ?  Have  any  of  the  observations 
made  on  milk  digestion  any  hygienic  significance? 

(15)  The  Diffusibility  of  the  Products  of  the  Artificial  Digestion 
of  Proteids.  From  the  products  of  digestion  in  experiments  (14,  b) 
digested  milk,  (13,  a)  digested  gelatin,  (13,  b)  digested  bread,  fill 
three  dialyzers — first  neutralizing  the  acid  with  sodic  carbonate. 
After  twelve  to  twenty-four  hours,  test  the  diffusate  for  peptone. 
Why  neutralize  the  liquid  before  filling  the  dialyzer? 

Have  all  of  these  indiffusible  proteids  been  wholly  or  in  part 
changed  to  diffusible  peptones  by  the  action  of  the  artificial  gastric 
juice  ? 

VIII.  THE  PROPERTIES  OF  FATS. 

1.  Materials.  Olive  oil ;  cream ;  butter;  beef -tallow;  lard;  adipose 
tissue,  and  cotton-seed  oil. 

2.  Experiments  and  Observations.  (1)  The  Osmic  Acid  Test. 
Place  in  test-tubes  a  small  amount  of  each  of  the  above  foodstuffs; 
add  to  each  a  few  cubic  centimetres  of  osmic  acid.  A  characteristic 
reaction  takes  place,  the  result  of  which  is  a  deep-brown  coloration 
of  the  fat.  If  the  conditions  are  favorable  the  stain  deepens  into  a 
sepia  black.  The  cream  and  the  adipose  tissue  have  proteid  admix- 
tures; note  the  variation  of  the  reaction. 

(2)  The  Solubility  of  Fats  and  Oils.  Prepare  three  tubes  each  of 
olive  oil  and  of  tallow;  treat  each  material  with  absolute  alcohol, 
with  ether,  and  with  chloroform.     It  will  be  found  that  all  of  these 


DIGESTION  AXD  ABSORPTION  I73 

reagents  are  solvents  of  fats  and  oils.  The  alcohol,  however,  dissolves 
very  much  more  of  the  fat  or  oil  when  warm  than  when  cold,  as  may 
be  demonstrated  by  making  the  alcoholic  solution  with  the  tube 
immersed  in  boiling  water;  after  the  alcohol  seems  to  have  reached 
the  limit  of  solution  at  that  temperature  immerse  the  tube  in  cold 
water.  A  large  part  of  the  dissolved  oil  instantly  separates  out,  but 
will  readily  redissolve  on  again  immersing  the  tube  in  the  boiling  water. 
(3)  The  Saponification  of  Fats  and  Oils,  (a)  To  about  2  c.c.  of 
olive  oil  in  a  test-tube  add  one  to  two  volumes  of  a  25  per  cent,  solu- 
tion of  sodic  hydrate.  Shake  the  mixture  vigorously;  it  is  evident  that 
a  chemical  reaction  is  in  progress.  The  fat  is  undergoing  the  process 
of  saponification.  A  complete  and  typical  saponification  requires  a 
more  careful  apportionment  of  the  amount  of  oil  and  of  alkali  used 
and  an  application  of  heat. 

(b)  Repeat  the  experiment,  substituting  a  25  per  cent,  solution  of 
potassic  hydrate.     The  result  is  similar. 

(c)  What  is  the  chemical  formula  of  palmitin?  Of  stearin?  Of 
olein  ? 

(3)  Write  the.  reaction  which  takes  place  in  saponification  of 
palmitin;  of  olein.  Note  the  ready  solubility  of  the  products  of  this 
reaction  in  water. 

(4)  To  a  solution  of  soap  add  any  aqueous  solution  of  a  calcium 
salt  soluble  in  water — e.  g.,  calcium  chloride;  a  curdy,  white  pre- 
cipitate separates  out.     Write  the  formula  of  the  reaction. 

]\Iay  the  reaction  have  any  relation  to  hygiene  or  therapeutics? 

(5)  The  Emulsification  of  Oils.  Gould  defines  an  emulsion  as 
*' water  or  other  liquid  in  which  oil  in  minute  subdivision  of  its 
particles  is  suspended."  One  may  add:  more  or  less  permanently 
suspended.  For  if  one  shake  together  vigorously  2  c.c.  of  oil  with 
an  equal  amount  of  water  in  a  test-tube  he  is  able  to  bring  about 
a  minute  subdivision  and  temporary  suspension  of  the  oil  in  the 
water.  While  the  oil  is  in  this  temporary  physical  condition  it  has 
the  white  color  typical  of  emulsions  in  general.  In  a  few  minutes, 
however,  the  particles  as  they  rise  to  the  top  of  the  liquid  coalesce 
into  minute  globules;  then  into  larger  and  larger  globules,  and  finally 
into  a  homogeneous,  supernatant  oil-layer. 

(a)  Add  to  the  mixture  above  described  2  or  3  c.c.  of  strained  egg 
albumin;  shake  vigorously.  One  observes  the  same  minute  sub- 
division of  the  particles,  but  they  show  no  tendency  to  coalesce  on 
standing;  the  suspension  is  more  or  less  'permanent. 

Why  do  not  the  particles  coalesce?  In  what  respects  is  this  emul- 
sion unlike  milk? 

(6)  To  2  c.c.  of  olive  oil  add  2  c.c.  of  siriipy  solution  of  any  gum 
— e.  g.,  gum  acacia;  shake  the  mixture  thoroughly.  An  enuilsion 
will  be  formed.  What  characteristics  has  this  emulsion  in  common 
"with  emulsion   fa)? 


174  SPECIAL  PHYSIOLOGY 

(c)  To  5  c.c.  of  cotton-seed  oil  containing  a  little  free  fatty  acid 
add  ten  drops  of  strong  sodium  carbonate  solution  and  shake.  A 
good  stable  emulsion  is  made  in  this  way. 

In  what  way  is  this  emulsion  different  from  those  which  precede? 
Which  one  of  the  emulsions  given  above  is  most  like  the  emulsions 
formed  in  the  small  intestine? 

(d)  What  materials  present  in  the  small  intestine  tend  to  promote 
emulsifi cation  of  fats? 

(6)  The  DifEusibility  of  Fats  or  Their  Derivatives  or  Modifications^ 
Fill  five  dialyzers  as  follows: 

(a)  Milk. 

(6)  Solution  of  soap. 

(c)  10  per  cent,  glycerin. 

(d)  Emulsion  (5,  a). 

(e)  Emulsion  (5,c). 

Complete  the  observations  on  the  following  day,  determining  what 
derivations  or  modifications  of  fat  or  oil  are  diffusible.  How  may 
the  presence  of  soap  in  the  diffusate  be  determined? 


IX.    INTESTINAL  DIGESTION. 

1.  Materials.     Two  pig  pancreases;  200  c.c.  of  pig  or  ox  bile. 

2.  Preparation.  (1)  Aqueous  Pancreatic  Extract,  (a)  Free  a  pig 
pancreas  of  fat. 

(6)  Grind  it  in  a  meat  hasher. 

(c)  Extract  with  water  kept  at  a  temperature  of  25°  to  28°  C. 

(d)  After  two  hours  strain  through  linen  and  filter  through  absorb- 
ent cotton. 

(2)  Glycerin  Extract  of  the  Pancreatic  Ferments,  (a)  After  freeing 
the  gland  of  fat  grind  it. 

(b)  Place  it  in  two  volumes  of  absolute  alcohol  for  two  days. 

(c)  Drain  off  the  alcohol  and  transfer  to  two  volumes  of  pure 
glycerin. 

(d)  After  one  week  press  out  the  glycerin,  which  has  extracted  the 
ferments. 

This  glycerin  extract  will  keep  indefinitely.  To  make  artificial 
pancreatic  juice  proceed  as  follows: 

(e)  To  one  volume  of  the  glycerin  extract  add  five  or  six  volumes 
of  water  and  sufficient  sodium  carbonate  solution  to  give  the  mixture 
a  distinctly  alkaline  reaction. 

(3)  Preliminary  Experiments  on  Bile.  This  secretion  may  easily  be 
procured  from  the  slaughter-house  at  almost  any  time  of  the  year. 

(a)  To  diluted  bile  add  dilute  acetic  acid.  The  copious  yellow 
precipitate  is  mucin. 

(6)  To  diluted  bile  add  absolute  alcohol;  mucin  is  precipitated; 


DIGESTION  AND  ABSORPTION  175 

filter.     To  one  portion  (I)  of   filtrate  add  HCl.     The  yellow  pre- 
cipitate is  glycocholic  acid. 

"To  the  other  portion  (II)  of  the  filtrate  add  lead  acetate,  which 
throws  down  lead  glycocholate.  Remove  this  by  filtration,  and  to  the 
filtrate  add  solution  of  basic  lead  acetate,  which  gives  a  further  pre- 
cipitation of  lead  taurocholate." — Chemical  Physiology,  Long,  p.  119, 

(c)  Gmelin's  Test  for  Bile  Pigments.  To  a  few  cubic  centimetres 
of  strong  nitric  acid  containing  nitrous  acid  carefully  add  dilute  bile. 
At  the  junction  of  the  liquids  a  play  of  colors,  green,  blue,  violet,  red, 
and  yellow,  will  be  noted;  the  green  being  next  to  the  bile  and  the 
yellow  next  to  the  acid.  This  delicate  and  most  reliable  test  may 
be  applied  to  any  liquid  suspected  of  containing  bile. 

(d)  The  reaction  of  bile  is  found  to  be  distinctly  alkaline. 

3.  Experiments  and  Observations.  (a)  The  Action  of  Pancreatic 
Juice  upon  Foods.  (1)  To  raw  or  cooked  starch  add  in  one  beaker 
aqueous  extract  of  pancreas  (a) ;  in  another  add  artificial  pancreatic 
juice  (6);  place  the  mixtures  in  the  incubator;  after  a  short  time 
test  for  reducing  sugar.   Pancreatic  juice  contains  an  amylolytic  jerment. 

(2)  Subject  fibrin  to  the  action  of  both  of  the  pancreatic  prepara- 
tions.    Pancreatic  juice  contains  a  'proteolytic  jerment. 

(3)  Boil  fresh  milk  and  mix  it  with  an  equal  bulk  of  the  aqueous 
extract  of  pancreas  and  put  the  mixture  into  the  incubator.  Put 
also  into  the  incubator  boiled  milk  diluted  with  an  equal  volume  of 
distilled  water.  The  milk  which  is  mixed  with  the  pancreatic  juice 
will  curdle  much  sooner  than  the  other.'  Pancreatic  juice  contains 
a  milk-curdling  ferment. 

(4)  ]Mix  5  c.c.  or  6  c.c.  of  neutral  olive  oil  with  an  equal  volume  of 
aqueous  extract  of  pancreas;  shake  the  mixture  vigorously.  No 
emulsion  is  formed.  Place  one-half  of  the  mixture  in  the  incubator. 
After  a  few  hours  any  undigested  oil  may  be  emulsionized  on  shak- 
ing, or  fresh  oil  may  be  emulsified.     Explain. 

(5)  To  the  second  part  of  the  mixture  add  3  c.c.  bile;  shake  the 
mixture  vigorously.  A  good  emulsion  is  formed.  How  is  this  emul- 
sion formed  ?  What  factor  of  an  emulsion  does  the  bile  add  ?  What 
is  the  relation  of  experiment  (5)  to  experiment  (4)  ?  Pancreatic  juice 
contains  a  fat-splitting  ferment  whose  action  liberates  fatty  acids. 

(h)  The  Action  of  Bile  upon  Foods.  (6)  To  starch  paste  add  several 
volumes  of  dilute  bile.    Result  ? 

(7)  To  fibrin  add  dilute  bile.     Result? 

(H)  To  oil  which  contains  free  fatty  acid  add  bile;  shake  the  mix- 
ture vigorously.     Result? 

CO)  To  neutral  oil  add  bile.;  shake  the  mixture  vigorously.  What 
is  the  result?  Allow  the  mixture  to  stand  in  the  incubator.  After 
several  hours  shake  the  mixture.    Is  an  emulsion  formed? 

nO)  Summarize  the  results  of  tlie  foregoing  experiments,  formu- 
lating a  series  of  cr)nclusions  regarding  the  action  of  jjuncreatic  juice; 
the  action  of  bile  and  their  combined  action  on  each  class  of  food. 


176  SPECIAL  PHYSIOLOGY 


ABSORPTION. 


Physiologists  have  entertained  the  hope  that  all  the  phenomena 
of  absorption  of  diffusible  substances  could  be  eventually  explained 
by  the  laws  of  physics.  That  hope  has  practically  given  place  to  the 
conviction  that  however  important  it  may  be  to  the  animal  economy 
to  produce,  in  its  digestive  processes,  diffusible  products,  these  products 
do  not  pass  through  the  epithelial  lining  of  the  alimentary  tract  at 
the  rate  or  in  the  proportions  that  would  be  observed  in  the  dialyzer. 
This  need  occasion  no  surprise;  in  one  case  we  have  to  deal  with 
living,  active  cells;  in  the  other  with  dead  tissue. 

Living  cells  of  muscle  tissue  or  of  gland  tissue  have  the  power  of 
selecting  from  the  tissue  plasma  such  materials  as  are  needed  for 
the  replenishment  of  their  substance.  Not  only  does  the  animal 
select  what  shall  be  taken  into  the  alimentary  tract,  but  the  epithelial 
lining  of  that  tract  seems  to  select  what  shall  be  absorbed  and  to 
absorb  it  according  to  laws  which  conform  not  at  all  to  the  laws  of 
osmosis. 

In  order,  however,  to  understand  the  current  literature  on  the  sub- 
ject of  absorption,  it  is  necessary  to  be  familiar  with  the  terminology 
and  the  laws  of  osmosis  and  dialysis.  To  that  end  the  student  may 
profitably  perform  for  himself  a  few  simple  experiments  preliminary 
to  more  complex  ones  which  the  demonstrator  may  suggest  or  may 
perform  for  the  class. 

1.  Appliances  and  Materials.  Six  dialyzers  complete,  includ- 
ing outer  receptacles  and  supports,  two  or  three  100  c.c.  evaporating 
dishes,  distilled  water,  sodium  chloride,  alcohol,  egg,  and  mercury 
manometer. 

2.  Preparation.  (1)  Fit  four  of  the  dialyzers  with  membrane  of 
pig  bladder.  The  bladders  should  be  carefully  selected  as  to  uni- 
formity in  thickness,  and  should  be  soaked  for  an  hour  or  more  in 
water  before  being  stretched  upon  the  dialyzers.  The  membrane 
should  be  stretched  as  nearly  uniform  as  possible  upon  four  dialyzers. 
Fit  one  dialyzer  with  parchment  paper,  such  as  is  frequently  used 
for  this  purpose.  Furnish  one  dialyzer  with  some  other  animal  mem- 
brane— e.  g.,  a  cow's  bladder  or  a  rabbit's  caecum. 

(2)  Prepare  dilute  egg  albumin  by  adding  to  strained  undiluted 
albumin  about  nine  volumes  of  distilled  water. 

3.  Experiments  and  Observations.  (1)  Salt,  in  saturated  aque- 
ous solution,  may  be  put  into  a  dialyzer.  So  adjust  the  apparatus 
that  the  water  in  the  outer  receptacle  shall  be  on  a  level  with  the 
solution  in  the  vertical  tube  of  the  dialyzer.  How  much  does  the 
water  rise  in  the  tube?  What  degree  of  positive  pressure  within  the 
dialyzer  does  that  represent?  How  much  pressure  per  unit  area, 
measured  with  a  mercury  manometer  will  it  be  necessary  to  produce 


DIGESTION  AND  ABSORPTION  177 

within  the  dialyzer  to  stop  the  increase  of  the  volume  of  its  contents  ? 
(Endosmotic  pressure.)  Will  that  amount  of  pressure  prohibit  diffu- 
sion between  the  liquids? 

(2)  After  osmosis  has  been  allowed  to  take  its  unimpeded  course 
for,  say,  one  hour,  starting  with  a  20  per  cent,  solution  of  NaCl  within 
and  distilled  water  without  the  dialyzer,  note  the  height  of  the  water 
in  the  tube  and  compute  the  number  of  grams  of  water  which  have 
entered  the  dialyzer.  Determine  how  much  NaCl  has  passed  out 
of  the  dialyzer.  An  easy  and  sufficiently  accurate  method  is  to  evap- 
orate to  dryness  all  or  a  known  proportion  of  the  liquid  in  the  outer 
receptacle,  and  weigh  the  dry  salt  remaining.  How  many  grams  of 
water  enter  the  dialyzer  for  each  gram  of  salt  that  leaves?  (Endos- 
motic equivalent. ) 

(3)  Is  the  endosmotic  equivalent  constant  for  salt  and  water? 
(a)  Is  it  the  same  for  different  strengths  of  the  salt  solution — i.  e., 

for  10  per  cent,  or  1  per  cent,  as  for  20  per  cent.  ?  (6)  Is  it  the  same 
for  two  hours  or  four  hours  as  for  one  hour? 

(4)  Fill  with  10  per  cent,  glucose  three  dialyzers  provided  with 
three  different  kinds  of  membrane.  Does  osmosis  take  place  at  the 
same  rate  in  all  three  dialyzers?  What  is  the  endosmotic  equivalent 
for  glucose? 

(5)  What  is  the  endosmotic  equivalent  for  dilute  egg  albumin? 
When  albumin  is  injected  into  the  colon  it  is  readily  absorbed  as 
albumin,  there  being  no  digestive  changes  in  it. 

(6)  Fill  a  dialyzer  with  equal  parts  of  10  per  cent,  glucose  and 
10  per  cent.  NaCl.  At  the  end  of  a  convenient  period,  two  to  six 
hours,  determine  whether  these  substances  have  diffused  according 
to  their  own  endosmotic  equivalents — i.  e.,  independent  of  each 
other,  or  have  they  been  influenced,  the  one  by  the  other? 


12 


CHAPTER  VII. 
VISION. 

I.    DISSECTION  OF  THE  APPENDAGES  OF  THE  EYE. 

Appliances.  Fresh  ox-eyes,  including  as  much  of  the  appendages 
as  possible;  physiological  operating  case;  dissecting  board  and  pins, 
such  as  used  for  frogs;  dog,  cat,  or  rabbit;  bone  forceps;  injection 
mass;  syringe. 

Dissection.     Follow  Cunningham  or  Quain,  vol.  iii.,  part  iii. 

(1)  Before  fixing  the  eye  to  the  board  make  a  careful  examination 
of  the  organ. 

(a)  Trace  the  conjunctiva,  describing  its  ocular  and  its  palpebral 
portions.  Describe  the  plica  semilunaris  and  the  caruncula.  Do 
these  two  tissues  have  the  same  relative  size  in  man  and  the  ox? 
Find  and  describe  the  puncta  lacrymalia.  Find  and  describe  the 
openings  of  the  lacrymal  ducts.  How  many  are  there?  Enumerate 
the  conjunctival  landmarks  which  determine  the  inner  from  the  outer 
side  of  the  eye.  Enumerate  the  conjunctival  landmarks  which 
determine  the  superior  aspect  of  the  eye.  Is  the  eye  which  you 
have  a  right  eye  or  is  it  a  left  one? 

(b)  Observe  the  appendages  of  the  eye.  Do  you  find  a  remnant 
of  the  levator  palpebrce  muscle?  Find  the  tarsal  cartilages  and  the 
remnant  of  the  orbicularis  palpebrarum  muscle.  Find  openings  of 
the  meibomian  and  of  sebaceous  glands.  Find  and  describe  the 
lacrymal  gland  as  to  location  and  size. 

Find  and  cut  off  ends  of  the  recti  and  oblique  muscles  of  the  eye. 

Describe  location  of  the  optic  nerve  with  respect  to  the  cornea. 

What  traces  have  you  found  of  the  capsule  of  Tenon? 

Enumerate  the  new  landmarks  which  determine  the  superior 
aspect  of  the  eye;  the  internal  aspect.  Are  these  extra  landmarks 
sufficient  to  determine  whether  the  eye  which  you  have  is  a  right 
or  a  left  one? 

(2)  Fix  the  eye  to  the  board  with  the  corneal  surface  down,  pinning 
down  flaps  of  the  conjunctiva  for  support. 

(a)  Dissect  out  the  four  recti  and  the  two  oblique  muscles.  One 
will  find  in  the  ox  a  rather  heavy  retractor  muscle  in  close  relation 
to  the  optic  nerve.  This  should  be  left  undissected  until  the  other 
muscles  are  demonstrated. 

(6)  Trace  the  intricate  loculi  of  the  capsule  of  Tenon. 


VISION  179 

(c)  Carefully  separate  from  the  eyeball  all  connective  and  adipose 
tissue. 

(3)  Remove  the  retractor  muscle  of  the  ox-eye  in  process  of  dis- 
section, taking  care  not  to  sever  any  important  bloodvessels  or 
nerves. 

(a)  Locate  and  describe  the  venw  vorticosce.  How  many  are 
there  ? 

(6)  Find  the  anterior  ciliary  arteries.     How  many  can  be  found? 

Describe  their  relation  to  the  tendons  of  insertion  of  the  recti 
muscles.     What  tissues  do  they  supply? 

(c)  Find  the  two  long  ciliary  arteries. 

(d)  Locate  and  enumerate  the  short  posterior  ciliary  arteries. 

(e)  Dissect  out  the  ciliary  nerves.    What  tissue  do  they  supply? 

(4)  Let  one  member  of  the  division  dissect,  for  demonstration,  the 
orbital  muscles  of  a  dog,  cat,  or  rabbit.  To  facilitate  the  dissection 
fix  the  animal  with  dorsum  up,  and  remove  with  bone  forceps  the 
upper  and  outer  walls  of  the  orbit. 

(5)  Let  one  member  of  the  division  inject,  with  carmine  or  ver- 
milion mass,  the  internal  carotid  of  a  dog,  cat,  or  rabbit,  and  dissect 
out  for  demonstration  the  ocular  branches  of  the  ophthalmic  artery. 


II.     DISSECTION  OF  THE  EYEBALL. 

Appliances.  The  eyes,  already  partly  dissected,  which  have  been 
kept  in  an  ice-chest.  Let  one  man  make  an  anterior  and  another 
a  posterior  dissection. 

Dissection.  L  Anterior  Dissection.  Fix  the  eye  to  the  board, 
cornea  upward,  pinning  out  the  dissected  muscles  as  guys. 

(Ij  Describe  the  cornea  as  seen  from  the  front.  Does  the  radius 
of  curvature  of  the  lateral  meridian  seem  to  be  the  same  as  that 
of  the  vertical  meridian?  With  heavy  scissors  remove  the  cornea, 
leaving  a  margin  of  one-sixteenth  inch  anterior  to  its  junction  with 
the  iris. 

Examine  the  cut  surface  of  the  cornea  with  a  lens. 

(2)  Through  the  elliptical  opening  thus  made  examine  the  iris  as 
to  texture,  etc. 

(3)  Holding  the  margin  of  the  cornea  with  strong  forceps,  carefully 
dissect  the  sclerotic  coat  from  the  choroid  for  about  one-eighth  of 
an  inch  posterior  to  the  angle  of  the  anterior  chamber.  liOcate  four 
points  in  the  margin  from  which  the  incisions  may  be  made  antero- 
posteriorly  between  the  insertions  of  the  recti  muscles.  From  the 
[joints  lof-ated  make  the  incisions  posteriorly  as  far  as  the  equator  of 
the  eycljall.  Dissect  each  flaf)  from  the  underlying  choroid;  remove 
the  pins  which  fix  the  recti  muscles,  and  through  traction  draw  the 
flaps  back;  fix. 


1 80  SPECIAL  PHYSIOL OGY 

(a)  Make  a  drawing  of  the  choroid  with  its  iridal  and  ciliary/ 
portions  thus  exposed. 

(6)  Locate,  if  possible,  the  course  and  distribution  of  nerves  and 
bloodvessels. 

(4)  With  fine  forceps  grasp  the  margin  of  the  iris  and  with  fine 
scissors  cut  out  a  sector  limited  posteriorly  by  the  ciliary  body. 

(a)  Study  the  boundaries  of  the  posterior  chamber. 

(b)  Find  fibres  of  the  suspensory  ligament. 

(c)  Describe  the  anterior  surface  of  the  ciliary  processes. 

(5)  Make  a  circular  incision  with  small  scissors  severing  the 
choroid  and  retina  at  about  the  line  of  the  ora  serrata.  Lift  off  from 
the  dense  vitreous  humor  the  whole  ciliary  apparatus  and  lens; 
place  them,  anterior  surface  downward,  upon  a  plate. 

(a)  Describe  the  posterior  aspect  of  the  ciliary  processes. 
(h)  Describe  the  lens  minutely,  as  viewed  externally, 
(c)  Make  a  section  of  the  lens;  describe  its  appearance.     Is  the 
capsule  discernible? 

(6)  Describe  the  retina  as  seen  through  the  vitreous  humor. 
(a)  Locate  the  entrance  of  the  optic  nerve. 

(6)  Can  the  fovea  centralis  be  located? 
2.  Posterior  Dissection. 

(7)  Let  one  member  of  the  division  remove  the  posterior  half  of 
the  sclerotic  coat,  after  fixing  the  eye  with  cornea  downward,  using 
the  recti  muscles,  in  this  case  also,  for  guys. 

(a)  Note  the  vence  vorticosce. 

(h)  Follow  the  ciliary  nerves  from  their  entrance  into  the  eyeball, 
along  their  course  between  the  sclerotic  and  choroid  coats. 

(c)  Do  you  find  the  long  ciliary  arteries,  or  the  posterior  ciliary 
arteries  ? 

(8)  Remove  the  choroid  carefully. 

(a)  Note  the  character  of  its  tissue,  its  vascularity,  and  its  rich 
pigmentation. 

(h)  Describe  the  retina  as  seen  from  this  direction.  Its  pigmented 
layer  has  probably  come  away  with  the  choroid. 

(9)  Remove  the  posterior  half  of  the  vitreous  body  together  with 
the  retina. 

Make  a  drawing  of  the  posterior  surface  of  the  lens,  suspensory 
ligaments,  and  ciliary  processes  as  shown  posteriorly. 

(10)  Remove  the  remnant  of  the  vitreous  body;  sever  the  fibres 
of  the  suspensory  ligament;  lift  out  the  lens. 

Describe  the  ciliary  body  and  the  iris  thus  held  in  their  normal 
relations  by  the  supporting  sclera. 


VISION 


181 


III.     PHYSIOLOGICAL  OPTICS. 

Determination  of  the  Indices  of  Refraction  of  Water  and  of 

Glass. 

1.  Appliances.  Apparatus  for  determining  the  index  of  refraction; 
a  deep,  flat-bottomed  water-pan;  a  cube  of  glass  4  to  6  cm.  in  linear 
dimensions  and  polished  on  at  least  two  opposite  sides  (the  two 
polished  sides  must  be  absolutely  parallel),  whether  the  other  sides 
are  parallel  or  polished  makes  no  difference;  centimetre  rule  and 
dividers. 

2.  Preparation.  A  very  convenient  and  sufficiently  exact  appa- 
ratus for  making  the  required  determination  may  be  readily  made  as 
follows : 

(1)  Take  a  carpenter's  tri-square,  constructed  wholly  of  iron; 
from  the  angle  x  (Fig.  76),  where  the  graduated  limb  joins  the 
body,  measure  off  centimetres  upon  the  inner  surface  of  the  body 
and  cut  them  in  with  a  file. 

Fig.  76 


Apparatus  for  determining  index  of  refraction. 


(2)  Locate  on  the  inner  edge  of  the  grachiated  limb  any  point, 
as  ?/,  6  to  0  cm.  from  the  point  x.  With  file  i-emove  about  ^  en), 
of  the  edge  as  indicated  in  figure,  cutting  deeply  at  z,  so  as  to  leave 
a  slender  point  at  //  as  indicated. 


182  SPECIAL  PHYSIOLOGY 

(3)  Drill  a  hole  in  the  inner  surface  of  the  body  at  o;  fit  and  drive 
a  heavy  brass  or  iron  wire  into  this;  sharpen  the  upper  end  of  the 
wire.  The  length  of  the  wire  above  the  body  must  be  2  or  3  cm. 
greater  than  the  distance  x  y.  Bend  the  point  over  so  that  distance 
o  p  shall  equal  x  y. 

3.  Experiments  and  Observations.  Place  the  instrument  in  the 
water-pan;  fill  the  pan,  so  adjusting  it  that  both  points  p  and  y  will 
just  touch  the  water,  or  rather  almost  touch  the  water,  for  the  surface 
of  the  water  at  y  must  be  absolutely  plane.  If  the  point  touch  it 
the  surface  will  not  be  plane. 

(1)  (a)  Bring  a  small  rule  {R)  into  position  and  clamp  it  to  the 
limb  of  the  instrument  by  means  of  heavy  serre-fine  forceps.  So 
adjust  the  rule  that  as  one  sights  along  its  upper  edge  the  points 
a,  y,  and  3  seem  to  lie  in  one  and  the  same  straight  line.  Lift  the 
apparatus  out  of  the  water  and  lay  it  on  the  table,  taking  care  not 
to  disturb  the  adjustment. 

(6)  With  dividers  measure  the  distance  from  the  point  y  to  line  3. 
This  is  the  radius.  Determine  the  point  where  the  circumference 
would  cut  the  upper  surface  of  the  rule — say,  point  h. 

(c)  From  this  point  determine  the  perpendicular  distance  to  the 
edge  of  the  limb  at  c. 

{d)  The  line  c  ?/  a:  is  a  normal  to  the  surface  of  the  water  at  the 
point  y.  The  angle  i  is  the  angle  of  incidence;  the  angle  r  is  the 
angle  of  refraction.  Imagine  a  circle  whose  centre  is  at  y  and  whose 
circumference  passes  through  h  and  3.  The  line  6  c  is  the  sine  of 
the  angle  of  incidence.  The  line  a:  3  is  the  sine  of  the  angle  of 
refraction. 

{e)  What  is  the  ratio  of  sine  i  to  sine  r,  or 


(2)  In  the  same  manner  determine  the  ratio  of  the  sines  of  these 
angles  when  the  rule  is  so  adjusted  as  to  bring  a'  ?/  4  in  apparently 
one  straight  line.    What  is  the  ratio  of  sine  i'  to  sine  /,  or 


sine  i^ 
sine  r'' 


(3)  If  the  instrument  has  been  carefully  constructed,  and  if  the 
determination  has  been  made  with  sufficient  care,  the  ratios  will  be 
found  to  be  practically  equal — i.  e., 


What  is  the  constant  ratio  in  the  case  of  water?  This  constant 
ratio  is  called  the  index  of  refraction  and  is  conventionally  repre- 
sented by  fJi. 


VISION  183 

For  water, 


sine  I      4 

=  „  =  1.333. 


sine  r      3 

(4)  To  determine  the  index  of  refraction  of  glass  proceed  as  in 
the  case  of  water.  Set  the  instrument  upon  the  table;  the  block  of 
glass  may  be  placed  upon  the  body  of  the  instrument,  the  polished 
surfaces  being  placed  above  and  below.  If  the  distance  between 
the  polished  surfaces  is  not  equal  to  x  y,  a  point  (y')  may  be  located 
on  the  upper  surface  near  the  edge  of  the  glass  block  by  making 
a  dot  with  ink  where  the  line  x  y  cuts  the  upper  surface  of  the  block. 
This  line  is  the  normal. 

What  is  the  index  of  refraction  of  the  glass  block  furnished  by 
the  demon.strator  ? 


IV.    TO  DETERMINE  THE  FOCAL  DISTANCE  OF  A  LENS;  THEN 
THE  USE  OF  THE  FORMULA 

1  +  1:=  1. 

0  ^  i         F 

An  easy  method  of  determining  the  focal  distance  of  a  lens 
depends  upon  the  relation  of  the  distance  of  the  conjugate  foci  to 
the  general  focal  distance.  This  relation  may  be  expressed  thus: 
The  sum  of  the  reciprocals  of  the  conjugate  foci  is  equal  to  the 
reciprocal  of  the  focal  distance. 

Now,  when  a  lens  throws  upon  a  screen  the  image  of  an  object 
it  is  evident  that  the  distance  of  the  object  (o)  represents  one  and 
the  distance  of  the  image  (i)  represents  the  other  of  these  conjugate 
focal  distances;  so  one  may  say:    The  reciprocal  of  the  distance  of 

the  object  from    the  lens  (-)  plus  the  reciprocal  of  the  distance  of 

the  image  (-)  equals  the  reciprocal  of  the  general  focal  distance  (— ) ; 
I  r 

thus  (^---f  _z=     ).   Xhis  formula  enables  one  to  compute  the  focal  dis- 
o      I      t 

tance  after  first  determining  by  experiment  the  values  o  and  i. 

1 .  Apparatus.     To  that  encl  one  may  construct  a  simple  apparatus 

(Fig.  77 j.     For  the  determination  of  the  focal  distance  it  is  usual 

to  have  both  object  and  lens  movable.     For  our  purpose  this  may 

be  dispensed  with,  as  it  lends  little  to  the  reliability  of  the  result 

and  detracts  much  from  the  simplicity  of  the  apparatus.     Construct 

from  half-inch  pine  boards  a  box  100  cm.  or  50  cm.  long  and  about 

8  cm.  high  and  wide  (inside  measurements).     The  box  should  be 

open  at  one  side.     The  inner  surface  of  one  end  may  be  painted 

white  and  serve  as  a  screen;  the  other  end   should  have  in  its  center 

a  large  hole.     Over  this  hole,  (;n  the  inner  surface  of  the  upright, 


184 


SPECIAL  PHYSIOLOGY 


fix  a  sheet  .of  lead  or  of  copper  in  which  some  figure  has  been  cut. 
Construct  a  lens  carrier  {c),  whose  pointer  (p)  will  indicate  upon 
the  scale  (/)  the  position  of  the  centre  of  the  lens.  The  use  of  the 
instrument  will  be  somewhat  facilitated  if  the  distance  between  the 
surface  of  the  screen  and  the  surface  of  the  lead  or  copper  be  pur- 
posely made  exactly  100  cm.  In  addition  to  the  above  apparatus 
one  needs  the  lenses  whose  focal  distance  he  is  so  determine.  He 
needs  also  a  lamp  or  candle  to  place  behind  the  metallic  screen  at  e. 


Fig.  77 


Apparatus  for  determining  the  principal  focal  distance  through  the  observation  of  the  con- 
Jugate  focal  distances :  o,  object ;  I,  lens ;  i,  image  (the  conjugate  focal  distances  o  I  and  i  I  may 
be  represented  by  o  and  i,  respectively) ;  c,  lens  carrier,  which  slides  along  the  guide  on  the 
bottom  of  the  box. 


2.  Experiments  and  Observations.  Place  a  light  behind  the 
metallic  screen;  it  shines  through  the  figure  cut  through  the  screen. 
This  figure  is  the  object  (o). 

(1)  (a)  Place  a  lens  in  the  carrier  and  so  adjust  it  that  the  plane 
which  it  represents  is  perpendicular  to  the  axis  of  the  instrument 
and  its  center  is  in  the  same  perpendicular  plane  with  the  index  (p) 
of  the  carrier. 

,(b)  Slide  the  carrier  along  the  base  until  the  object  is  sharply 
focused  upon  the  screen. 

(c)  Read  from  the  scale  the  distance  of  the  lens  from  the  image 
(i).    If  the  instrument  is  made  just  100  cm.  between  the  screen  and 
object,  then  the  difference  between  100  and  the  reading  will  be 
the  distance  of  the  lens  from  the  object.     Is  the  image  erect  or 
inverted?    Explain  the  phenomenon,  drawing  geometric  figure. 

(2)  Study  the  general  formula. 

1 
'F 


(a) 


^  +  -i 


(6) 

(c) 
id) 


F  =  . ;  but  0  +  i  =  100  ;  therefore 

o-\-i 

100  F  =  0  i 


F- 


n  I 

Too" 


From  this  form  of  the  statement  it  is  evident  that  the  lens  will 
throw  a  distinct  image  in  either  one  of  two  positions.  Demonstrate 
it  experimentally. 

(3)  Determine  o  and  i  for  each  lens  and  substituting  their  values 
in  the  equation  {d)  determine  the  value  of  F.    A  slight   deviation 


VISION  185 

may  be  expected  between  the  value  of  F  determined  from  the  above 
formula  and  that  determined  directly.  This  deviation  is  due  to  errors 
in  the  apparatus  and  in  the  observations. 

(4)  Problems.     The  value  of   the  formula  -  +  -.  =  _,  is  so  great 

o        I       F 

and  its  application  so  frecpient  that  the  student  should  thoroughly 

familiarize  himself  with  the  properties  of  lenses  as  revealed  in  this 

formula. 

Solve  the  following  problems: 

(1)  When  the  object  is  twice  the  focal  distance,  what  is  the  dis- 
tance of  the  image? 

(2)  When  the  distance  of  the  object  is  greater  than  2  F,  how  does 
the  distance  of  the  image  compare  with  2  Ff 

(3)  When  the  object  is  at  a  very  great  distance  (o=  oc),  at  what 
distance  will  the  image  be  formed? 

(4)  What  is  the  maximum  focal  distance  that  may  be  determined 
or  verified  with  the  above-described  apparatus? 

Discuss  in  detail. 


V.     TO   LOCATE   EXPERIMENTALLY   IN  THE  MAMMALIAN  EYE 

THE  CARDINAL  POINTS  OF  THE  SIMPLE 

DIOPTRIC  SYSTEM. 

In  the  study  of  the  glass  lens  one  takes  into  consideration  the 
index  of  refraction,  and  the  radius  of  curvature  of  the  surface  of  the 
lens.  When  one  remembers  that  the  eye  possesses  media  of  two 
different  refractive  indices,  bounded  by  three  curved  surfaces — 
anterior  corneal  surface  (radius  7.829  mm.),  anterior  and  posterior 
lens  surfaces  f radii  10  and  6  cm.,  respectively) — the  complexity  of 
the  problem  becomes  apparent. 

It  has  been  shown  mathematically  that  a  complex  optical  system 
consisting  of  several  surfaces  and  media,  centered  upon  a  common 
optical  axis,  may  l^e  treated  as  if  it  consisted  of  two  surfaces  only. 

Applying  this  principle  to  the  eye  it  has  been  found  that  the  several 
media  and  surfaces  may  be  reduced  to  two  parallel  spherical  surfaces 
whose  radii  are  5.215  mm.  These  surfaces  cut  the  optical  axis  just 
posterior  to  the  cornea  and  are  only  ^  mm.  apart. 

To  further  simplify  the  optics  of  the  eye  it  has  been  customary 
to  reduce  it  to  a  simple  dioptric  system  by  assuming  one  refracting 
surface  near  the  posterior  surface  of  the  cornea. 

A  Simple  Dioptric  System. 

The  simple  dioptric  system  is  one  in  wliic-h  tli<'  ray  passes  from  one 
medium    into   a  second   mcrhuin   of  different   refractive   index,   the 


186 


SPECIAL  PHYSIOLOGY 


surface  of  the  separation  of  the  two  media  being  a  spherical  surface. 
In  the  accompanying  figure  (Fig.  78)  the  spherical  surface  s's  p  s" 
separates  the  medium  m,  whose  refractive  index  is  1.000  from  the 
medium  m! ,  whose  refractive  index  is  1.500. 

Note  the  following  cardinal  'points  of  a  simple  dioptric  system. 

The  center  of  curvature  of  the  spherical  surface  (n)  in  the  nodal  point. 

That  radius  which  is  the  center  of  symmetry  of  the  dioptric  system 
{e.  g.,  n-p)  is  called  the  principal  axis  of  the  system.  In  this  axis 
lie  the  first  and  second  principal  foci,  f  and  /',  respectively.  The 
point  where  the  optical  axis  cuts  the  spherical  surface  p  is  called 
the  principal  point.  The  plane  tangent  to  the  spherical  surface  at 
this  point  is  the  principal  plane.  Planes  perpendicular  to  the  optical 
axis  at  /  and  /'  are  called  the  first  and  second  principal  focal  planes, 
respectively.    In  the  eye  the  second  principal  focal  plane  is  the  retina. 


Diagram  to  show  the  cardinal  points  of  a  simple  dioptric  system. 


1.  Appliances  and  Materials.  A  white  rabbit;  support  with 
universal  clamp  holder  and  small  cork-lined  burette  clamps;  metre 
stick  or  tape;  steel  or  ivory  rule,  with  millimetres  subdivided  if  pos- 
sible; hand  lens;  fine  dividers  with  needle  points;  bone  forceps; 
0.6  per  cent.  NaCl;  camel's-hair  pencil;  absorbent  cotton. 

1.  Preparation.  (1)  Mathematical.  (See  Fig.  79.)  We  wish  first 
to  locate  the  nodal  point  in  the  rabbit's  eye.  Represent  the  distance 
from  the  retina  to  the  nodal  point  by  n ;  the  distance  from  the  object 
to  the  image  by  d ;  the  vertical  dimension  of  the  object  by  o ;  the 
same  dimension  of  the  image  by  i.  From  the  similar  right  triangles 
of  the  figure  one  may  write: 


(1) 
(2) 

(3) 


:  i  z=  d  —  n  :  n. 
on  =  id  —  in; 

i  d 

o-\-i 


Under  the  conditions  of  the  experiment  i  is  so  small  compared 
with  0  that  it  may  be  ignored  in  the  denominator,  and  we  may  use 
the  equation: 

(4)  n  :=  '-^. 


VISION 


187 


2.  Arrangement  of  Apparatus,  (a)  A  convenient  object  to 
observe  is  a  well-illuminated  window,  or  one  sash  of  a  window. 
Measure  the  vertical  distance  between  the  horizontal  strips  of  the 
sash. 

(b)  Arrange  three  or  four  tables  end  to  end  in  a  line  perpendicular 
to  the  plane  of  a  window.  On  the  table  lay  off  from  the  plane  of 
the  window  the  distances  .5  m.,  5.5  m.,  and  6  m. 

3.  Operation.  (1)  Remove  an  eye  from  the  rabbit  which  has 
been  chloroformed  some  time  before  and  suspended  by  the  anterior 
limbs. 

(2)  Dissect  from  the  eye,  especially  from  the  posterior  aspect  of 
it,  all  of  the  areolar  connective  tissue,  muscle  tissue,  etc.,  down  to 
the  glistening,  smooth  sclera. 

(3)  Wrap  around  its  equator  a  band  of  absorbent  cotton  wet 
T\-ith  normal  solution. 


Fig.  79 


Diagram  of  the  dioptric  system  of  the  eye:  R,  point  where  visual  line  enters  cornea  ;  P,  prin- 
cipal point  of  dioptric  system  ;  y,  nodal  point ;  o,  object ;  i,  image ;  distance  o  N  and  i  N  may 
equal  o  and  i,  respectively. 

(4)  Fix  the  eye  in  the  clamp  with  its  axis  transverse  to  the  axis 
of  the  clamp,  taking  care  to  exert  ju.st  enough  pre.ssure  to  prevent 
the  eye  from  falling  on  being  touched,  but  not  enough  to  distort  it. 

(oj  Fix  to  the  clamp  a  thread  with  a  bit  of  lead  to  serve  as  a 
plumb  line. 

4.  Observations.  (1)  Adjust  the  support  so  that  the  eye  is  directed 
toward  the  object  and  the  image  is  located  approximately  symmetric- 
ally about  the  fovea  centralis  and  the  plumb  line  over  the  mark 
5  m.  With  the  fine  dividers  measure  in  the  image  the  distance 
between  tho.se  points  which  were  chosen  as  the  limits  of  the  ol)ject. 
The  value  of  this  measurement  may  be  read  to  tenths  of  millimetres 
by  laying  the  divider  points  upon  the  .steel  rule  and  reading  with 
the  hand  lens. 


188  SPECIAL  PHYSIOLOGY 

(2)  Make  similar  observations  at  5.5  m.  and  6  m.  Each  obser- 
vation should  be  made  three  or  four  times  and  the  average  taken. 

(3)  Record  these  averages  in  a  table  ruled  with  columns  for  the 
values  d,  o,  i  and  n. 

(4)  Calculate  for  column  n  the  values   obtained  by  substituting, 

id 
in  the  formula  n—  — ,  the  values  observed  in  (1)  and  (2).     What  is 
o 

the  value  oi  nf 

(5)  Measure  the  anteroposterior  diameter  of  the  eye.  How  far 
anterior  to  the  posterior  surface  of  the  sclera  is  n  located?  How 
far  from  the  surface  of  the  cornea?  How  does  the  ratio  of  these 
two  quantities  differ  from  that  given  above  for  the  human  eye? 

(6)  Is  the  image  erect  or  inverted?    Explain  the  phenomenon? 

(7)  Move  the  eye  to  within  1  m.  of  the  object.  Note  that  a  fairly 
clear  image  may  be  thrown  upon  a  posterior  segment  of  the  sphere, 
which  is  many  hundred  times  the  area  of  the  fovea  centralis. 

(8)  If  a  fine,  sharp  needle  be  thrust  through  the  eyeball,  following 
a  course  perpendicular  to  the  optical  axis  and  cutting  it  at  n,  what 
relation  would  this  needle  have  with  the  lens?  Would  it  be  tangent 
to  the  lens;  would  it  enter  the  lens,  or  would  it  pass  free  of  its  pos- 
terior surface? 

For  these  experiments  the  eye  may  be  frozen  after  the  introduction 
of  the  needle  and  a  vertical  longitudinal  section  made. 

VI.    ACCOMMODATION  AND  CONVERGENCE. 

In  the  above  experiment  with  the  excised  rabbit's  eye  one  notices 
a  marked  blurring  of  the  image  when  the  eye  is  brought  near  the 
object.  Though  the  definition  of  the  image  is  sharp  at  5  m.  to  6  m. 
or  beyond,  at  2  m.  or  3  m.  the  outlines  are  hazy.  The  normal  living 
eye  is,  however,  able  to  give  one  the  sensation  of  a  clear  image  at  any 
distance  from  several  inches  to  several  miles.  That  there  is  actually  a 
sharply  defined  image  upon  the  retina  when  the  normal  mind  has 
a  sensation  of  such  an  image  there  is  no  doubt. 

One  knows  from  his  experience  with  optical  instruments  that  they 
must  be  readjusted  for  each  distance  if  they  are  to  yield  a  sharp 
image  for  each  distance. 

The  same  thing  is  true  in  the  case  of  the  organic  optical  instru- 
ments with  which  one  perceives  the  form,  color,  and  space  relations  of 
the  objects  of  his  environment.  The  junctional  adaptation  of  the 
visual  organs  to  distance  is  called  accommodation. 

A.  Accommodation. 

Experiments  and  Observations.  (1)  Take  a  sharp-pointed  pen- 
cil or  similar  object  in  each  hand;  hold  the  upturned  points  in  the 


VISIOX 


189 


line  of  direct  vision  before  the  eye,  one  point  being  about  25  cm. 
distant  from  the  eve  and  the  other  at  arm's-length;  make  the  obser- 
vations with  one  eye,  the  other  being  closed  or  screened. 

(a)  Focus  upon  the  near  point.  Is  the  image  of  the  distant  point 
clear  ? 

(b)  Focus  upon  the  distant  point.  Is  the  image  of  the  near  point 
clear? 

(c)  While  the  eye  is  steadily  focused  upon  the  near  point  brino-  the 
distant  point  slowly  up  to  a  position  beside  the  near  point.  One  of 
the  images  is  transformed  from  an  illy  defined  one  to  a  clearly  defined 
one.  Which  image  is  it?  Does  one  note  a  similar  change  in  the 
definition  of  the  image  when  he  moves  the  near  point  out  to  a  posi- 
tion beside  the  distant  point  while  focusing  steadily  at  the  latter? 

(d)  Sum  up  the  results  of  the  experiments  into  a  concisely  formu- 
lated statement. 

(2)  Holding  the  points  side  by  side  at  a  distance  of  20  cm.,  note  that 
the  points  appear  equally  well  defined. 

(a)  Direct  the  eye  steadily  at  one  of  the  points  while  moving  the 
other  nearer  to  the  eye.  Note  the  number  of  centimetres  which  it 
advances  toward  the  eye  before  the  outlines  become  illy  defined. 
Reverse  the  act,  moving  the  point  back  to  its  original  position  beside 
the  stationary  point,  noting  that  the  image  of  the  receding  point 
remains  clear. 

(6)  Continue  to  carry  it  farther  from  the  eye,  noting  that  after  it 
has  been  carried  beyond  the  unmoved  focused  point  a  certain  dis- 
tance the  outline  becomes  illy  defined.  Note  the  number  of  centi- 
metres between  the  two  points  in  this  position. 

(c)  Make  a  similar  experiment,  using  30  cm.  for  the  distance  of 
the  stationary  point,  and  note  the  centimetres  between  the  points  at 
the  limits  of  clear  definition.  In  this  way  one  may  observe  and 
measure  the  focal  depth  of  the  eye. 

(d)  Is  the  focal  depth  greater  at  20  cm.  or  at  30  cm.  ? 

(e)  Tabulate  the  focal  depths  of  the  members  of  the  class  for  the 
distances  20  cm.,  30  cm.,  40  cm.,  50  cm.,  and  60  cm. 

(/)  Sum  up  the  results  of  the  experiment  into  a  concisely  formu- 
lated statement,  and  show  the  relation  between  ocular  focal  depth 
and  microscopic  focal  depth. 

Co)  Determination  of  the  Near  Point  or  "Punctum  Proximum."  Deter- 
mine the  distance  from  the  eye  of  the  nearest  point  at  which  a  pencil 
point  or  needle  may  be  perfectly  clearly  seen.  The  exact  location  of 
the  near  point  may  h)e  more  satisfactorily  determine*  1  if  one  look  at 
the  object  through  two  pinholes,  2  mm.  apart,  in  a  card.  At  this 
point — the  punctum  proximum — the  act  of  accommodation  is  brought 
actively  into  play. 

(4)  Determination  of  the  Punctum  Remotum.  (a)  Direct  the  eye 
toward   some  object  not  Ics.s  than  0  iii.  away  and  describe   to   the 


190  SPECIAL  PHYSIOL OGY 

other  members  of  the  class  the  minute  details  of  the  object,  such  as 
slight  irregularities  of  surface  lines  or  other  details.  If  an  individual 
is  able  to  convince  his  comrades  that  he  can  perceive  at  this  distance 
the  minute  details  of  objects,  he  must  be  credited  with  normal  vision. 
Inasmuch  as  he  can  also  see  with  the  usual  distinctness  more  distant 
objects,  the  punctum  remotum  is  said  to  be  located  at  infinity;  or, 
to  state  it  in  another  way,  the  eye  is  able,  with  suspended  accommo- 
dation, to  bring  parallel  rays  to  a  focus  upon  the  retina. 

(6)  It  frequently  happens  that  the  individual  under  observation 
fails  to  make  out  more  than  the  merest  outline  of  an  object  6  m. 
away.  Decrease  the  distance  until  he  is  able  to  perceive  details  seen 
by  the  majority  of  his  comrades.  If  this  distance  has  to  be  decreased 
to  2  m.  or  3  m.  the  determination  may  be  made  more  exact  by  resort- 
ing again  to  the  needle  and  punctured  card  mentioned  in  (3),  and 
carrying  the  needle  away  until  it  appears  double. 

In  recording  the  punctum  remotum,^  write  infinity  ( oo)  for  6  m. 
or  more,  and  for  any  distance  within  that  record  in  metres  and 
decimals  thereof. 

(5)  How  many  metres  from  the  punctum  remotum  to  the  punctum 
proximum  in  those  cases  where  the  punctum  remotum  is  less  than 
6  metres? 

(6)  Observe  the  pupil  closely  while  the  subject  directs  the  eye  from 
a  distant  object  to  a  near  one.  It  contracts  slightly.  One  may  assume 
that  this  act  of  the  iris  is  advantageous.  Show  from  the  standpoint 
of  theoretical  optics  why  it  is  advantageous. 

(7)  Observe  from  the  side  that  when  the  act  of  accommodation 
takes  place  the  iris  at  the  edge  of  the  pupil  not  only  moves  toward  the 
center,  but  advances  noticeably  toward  the  cornea.  What  could 
produce  this? 

(a)  If  the  edge  of  the  iris  rests  upon  the  lens  capsule,  would  it  not 
be  pushed  farther  toward  the  cornea  incident  to  its  contraction  toward 
the  center? 

If  the  pupil  contracted  from  a  3  mm.  diameter  to  a  2  mm.  diameter, 
how  much  would  it  advance  incident  to  the  normal  curvature  of  the 
lens  (radius  10  cm.)?  Could  this  be  detected  by  the  method  of 
observation  which  has  been  employed? 

(6)  Account  for  the  forward  movement  of  the  pupillary  edge  of  the 
iris  during  accommodation. 

B.  Adaptation  of  the  Eye  for  Direction.    Convergence. 

Just  as  the  eye  possesses  a  mechanism  by  which  it  changes  its 
refractive  power  for  different  distances,  so  it  possesses  a  mechanism 

1  It  must  be  stated  here  that  this  experiment  does  not  make  it  certain  that  the  punctum 
remotum  is  not  beyond  infinity.  This  would,  however,  be  a  pathological  condition,  and 
need  not  be  discussed  here.  There  will  be  occasion  to  refer  to  this  question  more  in  detail 
in  a  subsequent  lesson. 


VISION  191 

by  which  it  may  change  the  direction  of  its  visual  axis  from  one  object 
to  another  or  may  follow  the  movements  of  objects  within  the  range 
of  vision. 

1.  Monocular  Fixation.  Let  two  individuals  work  together,  one 
as  subject  and  the  other  as  observer.  Let  them  sit  on  opposite  sides 
of  the  table.    Let  the  subject  close  or  screen  one  eye. 

(1)  Hold  any  object  directly  in  front  of  the  subject;  let  the  subject 
keep  his  gaze  continually  fixed  upon  the  object.  Move  the  object 
quickly  toward  the  subject's  left,  and  note  the  fixation  anew  of  the 
object  in  its  new  position.  What  muscle  or  muscles  accomplished  this 
act  of  rrionocular  fixation? 

(2)  Move  the  object  quickly  in  the  opposite  direction ;  then  upward, 
downward,  diagonally,  noting  the  instantaneous  adaptation  of  the  eye 
to  the  new  direction,  recording  also  the  muscle  or  muscles  involved  in 
each  act.    Are  all  the  movements  apparently  equally  ready  and  exact? 

(3)  Bringing  the  object  to  a  point  directly  in  front,  1  m.  distant, 
note  through  how  great  a  lateral  movement  it  may  be  carried  without 
inducing  any  discernible  change  in  the  visual  axis  of  the  eye. 

(4)  Bring  the  object  to  the  central  position  and  move  it  very  slowly 
outward  in  any  direction,  noting  whether  the  changes  in  the  direction 
of  the  visual  axis  are  equally  slow  and  regular. 

2.  Binocular  Fixation.  In  the  above  experiments  it  was  probably 
noted  by  both  sul)ject  and  observer  that  the  closed  or  screened  eye 
responded  to  every  movement  of  the  other  eye. 

(5)  With  both  eyes  open  and  fixed  upon  an  object  held  directly  in 
front  at  a  distance  of  about  1  m.,  let  the  observer  move  the  object 
quickly;  then  slowly,  right,  left,  up,  down,  and  around,  and  observe 
the  continuous  perfect  fixation  of  the  object  with  both  eyes. 

(a)  What  muscles  are  involved  in  following  an  object  from  one's 
right  side  to  his  left?    In  each  other  direction  in  turn? 

(h)  Do  all  these  muscles  seem  to  act  perfectly  in  all  of  the  subjects 
examined?    If  not,  describe  any  variation. 

3.  Convergence,  (a)  Let  the  subject  direct  his  gaze  at  the  tip  of 
the  observer's  ear,  and  without  warning  change  his  point  of  binocular 
fixation  to  some  distant  object  in  the  same  line  of  vision.  What  change 
in  the  eyes  of  the  subject  is  noticeable  by  the  observer?  What 
muscles  were  involved  in  producing  the  change? 

(b)  Hold  an  object  in  front  of  the  subject  and  1  m.  distant.  Move 
it  directly  toward  the  subject's  eyes  and  note  the  convergence  of  the 
lines  of  vision  of  the  two  eyes.    What  muscles  perform  the  act? 

(c)  Through  how  short  a  distance  may  the  object  be  moved  in 
the  direct  line  of  vision  without  causing  a  discernible  change  of  the 
angle  of  convergence  of  the  two  eyes. 

(d)  From  the  central,  1  m.  position,  carry  the  object  to  a  point 
about  \  m.  to  the  right  and  i  m.  above  the  eyes  of  the  subject.  What 
muscles  are  involved  in  the  act  of  convergence? 


192  SPECIAL  PHYSIOLOGY 

(e)  Is  the  power  of  convergence  apparently  normal  in  all  members 
of  the  class?    If  not,  describe  minutely  any  variations. 


VII.  MISCELLANEOUS  EXPERIMENTS. 

(a)  Schemer's  Experiment.  (1)  Prick  two  smooth  holes  in  a  card 
at  a  distance  from  each  other  less  than  the  diameter  of  the  pupil. 
Fix  two  long,  fine  needles  or  straws  in  two  pieces  of  wood  or  cork. 
Fix  the  cardboard  in  a  piece  of  wood  with  a  groove  made  in  it  with 
a  fine  saw,  and  see  that  the  holes  are  horizontal.  Place  the  needles 
in  line  with  the  holes,  the  one  about  eight  inches,  the  other  about 
eighteen  inches  from  the  card. 

(2)  Close  one  eye,  and  with  the  other  look  through  the  holes  at  the 
near  needle,  which  will  be  distinctly  seen,  while  the  far  needle  will  be 
double,  both  images  being  somewhat  dim. 

(3)  With  another  card,  while  accommodating  for  the  near  needle 
close  the  right-hand  hole,  the  right-hand  image  disappears,  and  if  the 
left-hand  hole  be  closed  the  left-hand  image  disappears. 

(4)  Accommodate  for  the  far  needle,  the  near  needle  appears 
double.  Now  close  the  right-hand  hole,  and  the  left-hand  image 
disappears;  and  on  closing  the  left-hand  hole  the  right-hand  image 
disappears.     (Practical  Physiology,  Stirling.) 

(5)  Explain  the  phenomena,  drawing  figures  which  show  just  what 
must  take  place  in  the  eye. 

(fe)  The  Blind  Spot.  (6)  Marriotte's  Experiment.  On  a  white 
card  make  a  black  cross  and  a  circle  about  three  inches  apart. 
Closing  the  left  eye  hold  the  card  vertically  about  ten  inches  from 
the  right  eye,  so  as  to  bring  the  cross  to  the  left  side  of  the  circle. 
Look  steadily  at  the  cross  with  the  right  eye,  when  both  the  cross  and 
circle  will  be  seen.  Gradually  bring  the  card  toward  the  eye,  keeping 
the  axis  of.  vision  fixed  upon  the  cross.  At  a  certain  distance  the 
circle  will  disappear — i.  e.,  when  its  image  falls  on  the  entrance  of 
the  optic  nerve.  On  bringing  the  card  nearer  the  circle  reappears, 
the  cross,  of  course,  being  visible  all  the  time. 

(7)  Map  Out  the  Blind  Spot.  Make  a  cross  on  the  center  of  a  sheet 
of  white  paper  and  place  it  on  a  table  about  ten  or  twelve  inches  from 
you.  Close  the  left  eye  and  look  steadily  at  the  cross  with  the  right 
eye.  Wrap  a  penholder  in  white  paper,  leaving  only  the  tip  of  the 
penpoint  projecting,  dip  the  latter  in  ink,  or  dip  the  point  of  a  white 
feather  in  ink,  and  keeping  the  head  steady  and  the  axis  of  vision 
fixed,  place  the  penpoint  near  the  cross  and  gradually  move  it  to 
the  right  until  the  black  becomes  invisible.  Mark  this  spot.  Carry 
the  blackened  point  still  farther  outward  until  it  becomes  visible  again. 
Mark  this  outer  limit.  These  two  points  give  the  outer  and  inner 
limits  of  the  blind  spot.    Begin  again,  moving  the  pencil  first  in  an 


VISION  193 

upward  and  then  in  a  downward  direction,  in  each  case  marking 
where  the  pencil  becomes  invisible.  If  this  be  done  in  several  diam- 
eters an  outline  of  the  lilind  spot  is  obtained,  even  little  prominences 
showing  retinal  vessels  being  indicated. 

(S)  To  Calculate  the  Size  of  the  Blind  Spot.  Helmholtz  gives  the  fol- 
lo\\ang  formula  for  this  purpose:  \Vhen  /  is  the  distance  of  the  eye 
from  the  paper,  F  the  distance  of  the  second  nodal  point  from  the 
retina  (usually  15  mm.),  d  the  diameter  of  the  sketch  of  the  blind  spot 
drawn  on  the  paper,  and  D  the  corresponding  size  of  the  blind  spot: 

Determine  the  diameter  of  the  blind  spot  (D)  for  each  member 
of  the  class. 

VIII.    PERIMETRY. 

In  the  foregoing  experiments  we  have  dealt  exclusively  with  what 
is  called  direct  vision — i.  e.,  with  phenomena  involving  the  formation 
of  a  clearly  defined  image  upon  the  macula  lutea.  Everyone  has 
noticed  that  outside  the  range  of  direct  vision  one  may  still  get  a 
pretty  definite  idea,  not  only  of  form,  but  of  color  as  well.  It  is  the 
purpose  here  to  ascertain  just  how  far  this  axis  of  indirect  vision 
extends  in  every  direction  from  the  visual  axis,  or  to  locate  the 
perimeter  of  the  field  of  indirect  vision.  Various  instruments  have 
been  devised,  called  perimeters,  to  aid  one  in  perimetry. 

All  of  these  appliances  have  for  their  object  the  mapping  of  the 
field.  In  all  exact  methods  the  map  takes  the  form  of  a  polar  map, 
the  pole  corresponding  to  the  point  where  the  line  of  vision  would 
pierce  perpendicularly  the  plane  of  the  map. 

1.  Appliances.  A  perimeter,  or  ruled  blackboard  (Fig.  81); 
perimeter  charts,  such  as  shown  in  Fig.  82. 

2.  Preparation.  A  very  economical  and  accurate  perimeter  may 
be  constructed  in  the  following  manner: 

Take  a  blackboard  whose  dimensions  are  about  1  m.  by  1.5  m.; 
locate  a  point  40  cm.  from  one  end  and  50  cm.  from  either  side.  Let 
this  be  the  point  of  fixation  or  the  point  where  the  line  of  direct  vision 
falls  U[jon  the  surface  of  the  board. 

We  propose  now  to  draw  upon  the  boaixl  a  series  of  circles  whose 
distance  from  one  another  shall  represent  an  angular  distance  of 
10  flegrees.  Reference  to  Fig.  80  makes  it  evident  that  if  the  line  A  B 
represents  the  plane  surface  of  the  blackboard,  and  if  tiie  eye  be  j)laced 
at  O,  the  efjual  increments  of  10  degrees  on  the  (jua<irant  become  a 
.series  of  increasing  increments  upon  the  surface  of  the  board.  The 
numbers  at  the  right  (Fig.  80)  show  just  how  many  centimetres  the 
radius  of  each  successive  circle  should  be,  j)rovidcd  the  distance  of 
the  eye  from  the  board  be  taken  at  20  cm. 

13 


194 


SPECIAL  PHYSIOLOGY 


After  drawing  the  circles,  draw  meridians,  which  divide  each 
quadrant  into  three  to  nine  subdivisions.  The  complete  blackboard 
chart  will  have  the  appearance  and  proportions  shown  in  Fig.  81. 
The  circles  and  meridians  should  be  traced  permanently  in  white 
enamel  upon  the  surface  of  the  blackboard.  Any  marks  upon  the 
board  with  chalk  may  then  be  erased  without  disturbing  the  perim- 
eter circles. 

The  most  satisfactory  test  objects  are  pieces  of  fresh  crayon  not 
over  1  cm.  in  length.  They  may  be  held  in  wire  holders  of  convenient 
length. 


Fig.  80 


Fig.  81 


Each  blackboard  must  be  provided  with  a  rest  or  contrivance  to 
ensure  that  the  subject's  eye  is  20  cm.  from  the  surface  of  the  board. 
Whether  this  takes  the  form  of  a  rod  of  wood  extending  out  from  the 
board  and  so  adjusted  that  when  the  subject  rests  the  most  prominent 
infraorbital  region  upon  its  end  the  cornea  will  he  20  cm.  from  the 
center  of  the  chart,  or  whether  it  takes  some  other  form  that  ensures  the 
same  results,  is  of  little  consequence. 

3.  Experiments  and  Observations.  In  all  the  observations  which 
are  subsequently  indicated  it  is  taken  for  granted  that  the  visual  axis 
is  perpendicular  to  the  surface  of  the  chart,  that  the  center  of  the 
chart  is  the  point  of  fixation,  and  that  the  accommodation  is  kept 
uniform — i.  e.,  the  eye  is  either  uniformly  focused  on  the  center  of  the 
blackboard  perimeter  or  uniformly  relaxed ;  further,  that  the  eye  not 
under  observation  be  closed  or  closely  shaded. 


VISION 


195 


(1)  Examine  the  upper  median  quadrant  by  sweeping  a  white  test 
object  around  arc  60  degrees,  keeping  the  test  object  as  near  the 
surface  of  the  chart  as  possible.  If  the  subject  does  not  see  it  at 
all,  try  latitude  50  degrees.  Having  located  the  circle  which  seems 
to  be  near  the  boundary,  locate  upon  each  meridian  a  point  which 
indicates  the  limit  of  indirect  vision  in  that  direction.  Join  with  a 
continuous  line  the  points  located,  thus  enclosing  an  area  of  indirect 
vision. 

(2)  Test  the  lower  median  quadrant  in  the  same  way.  Is  the  total 
area  covered  by  indirect  vision  in  this  quadrant  greater  or  less  in 
extent  than  that  in  the  upper  quadrant? 


270° 


Perimeter  chart,  uix)n  which  the  blackboard  perimeters  are  to  be  transcribed  for  permanent 

record. 


.  (3)  Test  the  upper  lateral  quadrant  and  then  the  lower  lateral 
quadrant.  Are  these  two  quadrants  practically  equal?  Is  there  any 
ready  explanation  why  the  outer  two  c|uadrants  should  contain  such 
an  excess  of  area  over  the  inner  two  (|ua(h'ants? 

(4)  To  Record  the  Perimeter  Outline.  For  this  purpose  one 
should  liuvc  printed  charts  like  the  one  given  in  Fig.  S2.  Note  that 
here  the  circles  are  equidistant.  They  represent  concentric  arcs  of  a 
quadrant  with  10  degrees  of  tlie  circle  between  each  two,  while  the 
circle  uptjn  the  bhickboard  chart  represents  a  radial  projection  of  these 
arcs  upon  a  plane  tangent  to  the  sphere  at  the  point  of  fixation. 

In  transcribing  the  perimeter  upon  tiie  record  chart  one  has  only 


196  SPECIAL  PHYSIOLOGY 

to  locate  the  twelve  or  more  points  located  upon  the  observation  chart 
and  join  these  points  into  a  continuous  perimeter. 

(5)  In  the  above  experiment  we  have  determined  the  perimeter  for 
light  sensation  only;  the  subject  being  conscious  simply  of  a  light  or 
white  spot  on  a  dark  ground,  but  not  certain  whether  the  spot  is 
circular  or  square. 

(6)  Determine  and  chart  various  color  perimeters:  (a)  red,  ih) 
green,  and  (c)  blue. 

Have  the  color  perimeters  the  same  general  form  as  the  white 
perimeters?  If  not,  describe  any  noticeable  variations.  Which  of  the 
color  perimeters  encloses  the  greatest  area  ?  Enumerate  them  in  order 
of  area.  Is  this  the  order  which  one  would  expect?  Give  grounds 
for  position. 

(7)  Take  corresponding  perimeter  for  the  other  eye.  To  use  the  same 
blackboard  it  will  be  necessary  to  turn  it  the  other  edge  up.  In  what 
general  respect  do  the  right  perimeters  differ  from  those  of  the  left? 

(8)  With  the  help  of  light  perimeters  of  the  right  and  left  eyes, 
determine  the  field  of  binocular  vision.  This  is  the  field  of  binocular 
indirect  vision. 


IX.     DETERMINATION  OF  NORMAL  VISION. 

The  Acuteness  of  Direct  Vision. 

1.  Appliances.  Charts  printed  with  Snellen's  test  type,  astigmatic 
chart,  and  test  lenses  of  following  strength:  +  0.50  D.,  +  0.75  D., 
+  1.00  D.,  +  2.00  D.,  +  3.00  D.,  —0.50  D.,  —0.75  D.,  —1.00  D., 
—2.00  D.,  —3.00  D.,  +1.00  D.  cyl.,  +2.00  D.  cyl.,  —1.00  D.  cyl., 
— 2.00  D.  cyl.;  simple  test  frames  and  shade;  Holmgren's  worsteds. 

2.  Preparation.  Preparatory  to  testing  normal  vision  it  is  neces- 
sary to  make  a  few  general  statements. 

(1)  The  Numeration  of  Lenses.  The  refractive  power  of  a  lens 
is  the  reciprocal  of  its  focal  distance.  The  refractive  power  of  a  lens 
whose  focal  distance  is  1  m.  is,  for  example,  only  one-half  as  great 
as  that  of  a  lens  whose  focal  distance  is  0.5.  Monoyer  introduced 
the  term  dioptre  as  a  unit  in  measuring  lenses.  One  dioptre  (1  D.) 
represents  the  refractive  power  of  a  lens  whose  focal  distance  is  1  m.; 
2  D.  corresponds  to  ^  m.;  3  D.  to  ^  m.;  4  D.  to  i  m.,  etc.;  0.5  D. 
represents  the  refractive  power  of  a  lens  of  2  m.  focal  distance; 
0:25  D.  of  4  m.  focal  distance,  and  0.125  D.  of  8  m.  focal  distance. 
If  the  lenses  are  convex  (biconvex)  a  plus  sign  is  prefixed  to  the 
number — i.  e.,  +5  D.  means  a  biconvex  lens  of  5  dioptres  refractive 
power,  or  ^  m.  focal  distance.  While  —  5  D.  means  a  biconcave  lens 
of  1^  m.  negative  focal  distance. 

The  use  of  the  cylindrical  lenses  is  frequently  necessary.  A 
cylindrical  lens  is  a  section  of  a  cylinder  parallel  to  its  axis. 


VISION 


197 


Cylindrical  lenses  may  be  convex  or  concave.  A  convex  cylindrical 
lens  capable  of  bringing  rays  to  a  linear  focus  at  a  distance  of  |  m. 
would  be  designated  as  follows:  2  D.  cyl. 

(2)  Test  Types  and  Visual  Angle.  The  visual  angle  is  that  in- 
inchided  between  lines  joining  the  extremities  of  an  object  and  the 
nodal  point,  or  the  angle  subtended  by  an  object  at  the  nodal  point. 

Fig.  83 


Illustrating  the  visual  angle  (v)  and  the  relation  of  the  distance  (d)  to  the  length  of  the  object  (o) 
and  image  (i).    N,  the  nodal  point ;  n,  the  focal  distance,  the  image  being  on  the  retina. 

In  Fig.  83  the  object  at  o  subtends  the  angle  v,  while  the  object  at 
O,  though  much  larger,  subtends  the  same  angle  v.  Now  it  has  been 
determined  by  Snellen  that  the  normal  eye  distinguishes  letters 
subtended  by  an  angle  of  5  minutes.  If  we  let  d  equal  distance  of 
object  from  nodal  point,  n  equals  distance  of  image  from  nodal 
point,  i  length  of  image,  and  o  of  object,  then 


(1) 

(2) 

(3) 
(4) 


but 


■  :  0  :  :  n  :  d  ; 

0  =    ~  a  : 
n 

sine  V 

COS.   V 

0  ^  d  tan.  V, 


tan.  V, 


The  tangent  of  5'  =  0.001454;  assume  rf=l  m.  (1000  mm.),  what 
is  the  height  of  the  smallest  letter  discernible  to  the  average  normal 
eye  at  that  distance? 

At  1  m.  height  of  letter,  0  =  0.00145+1000=1.45  mm. 

Determine  the  height  for  each  of  the  following,  respectively:  60  m., 
30  m.,  20  m.,  15  m.,  12  m.,  9  m.,  6  m.,  4.5  m.,  3  m.,  2.5  m.,  2  m., 
1.5  m.,  1  m.,  0.75  m.,  0.50  m. 

What  is  the  size  of  the  image  in  all  these  cases?  A  cultivation  of 
the  visual  power  of  the  eye  may  reacHly  in  the  emmetropic  eye  bring 
up  its  definition  to  \  above  the  average  or  so  that  the  minimum 
visual  angle  for  acute  vision  equals  4'. 

3.  Experiments  and  Observations.  (I)  To  Test  the  Form  Sense. 
In  all  of  the  tests  licrc  described  it  is  understood,  unless  otherwise 
stated,  that  the  subject  sit  directly  facing  the  chart,  which  should  be 
6  m.  distant  and  well  illuminated. 


198  SPECIAL  PHYSIOLOGY 

(1)  Let  the  subject  put  on  the  test  frames  with  the  left  eye  shaded, 
and  direct  the  right  eye  to  the  letters  of  the  line  marked  6  m.  These 
letters  in  their  vertical  dimension  subtend  an  angle  of  5'.  The 
average  normal  eye  will  be  able  to  recognize  easily  every  letter  in 
the  line.  Should  there  be  any  hesitation  in  the  differentiation  of 
C  from  G,  of  P  from  D  or  F,  of  K  from  X,  etc.,  make  a  note  of  it; 
its  significance  will  be  apparent  later. 

In  recording  the  acuteness  of  vision  one  compares  the  minimum 
angle  of  distinct  vision  in  the  subject  under  observation  with  the 
normal.  If  the  subject  reads  readily  at  6  m.  he  is  credited  with 
normal  vision  or  with  a  minimum  visual  angle  normal  or  unity. 
This  is  expressed  in  the  following  manner:  Let  V  equal  visual 
acuteness;  d,  the  distance  from  the  chart;  D,  the  distance  at  which 

the  type  should  be  read:  F=  — .    In  the  above  case  F=-or  1 — i.e., 

normal  vision. 

(2)  Suppose  that  the  subject  cannot  read  the  6  m.  line  readily, 
let  him  try  the  line  above.    If  he  reads  that  readily  his  visual  acute- 

ness  would  be  F=— =-,  two-thirds  normal.     It  is  usual,  however, 

not  to  reduce  the  fraction,  but  to  use  the  6  as  the  numerator  always. 

(3)  How  shall  one  express  visual  acuteness  for  an  individual  who 
reads  at  6  m.  what  he  should  read  at  21  m.  ?  At  24  m.  ?  At  30  m.  ? 
At  4.5  m.?    At  3  m.? 

(4)  How  many  members  of  the  class  have  a  visual  acuteness 
greater  than  unity?  May  a  visual  acuteness  above  the  normal  be 
attributed  in  any  degree  to  cultivation  of  the  vision,  or  is  it  to  be 
interpreted  solely  as  a  natural  endowment? 

(5)  Let  a  subject  take  a  seat  6  m.  distant  from  the  chart.  Hold 
before  his  eye  a  +0.75  D.  lens,  it  will  probably  make  indistinct  and 
blurred  distant  objects  which  were,  without  the  lens,  clear,  (a)  If 
such  be  the  case  it  is  likely  that  refraction  of  the  eye  is  normal,  and 
for  our  purpose  it  may  be  recorded  as  an  emmetro'pic  eye. 

(b)  If,  however,  the  vision  remains  perfectly  clear  for  distant 
objects,  with  +0.75  D.  or  the  +1  D.  lens  before  the  eye  it  is  evident 
that  the  refraction  of  the  eye  is  not  normal. 

(c)  Suppose,  on  the  other  hand,  that  distant  objects  cannot  be 
clearly  seen  with  the  unaided  eye,  but  with  the  help  of  concave 
lenses  clearly  seen,  it  is  evident  again  that  the  refraction  of  the 
eye  is  abnormal. 

(6)  In  case  (5,  c)  where  were  the  parallel  rays  focused  when  the 
concave  lens  was  used  ?  Where  were  the  parallel  rays  focused  in  the 
unaided  eye  ?  Would  it  be  possible  for  the  condition  to  be  corrected 
by  an  exercise  of  the  accommodation  ?  If  the  punctum  remotum  is 
2  m.,  and  if  the  refractive  indices  and  curvatures  of  the  refracting 


VISION  199 

surfaces  are  all  normal,  in  what  way  must  the  eye  differ  from  the 
normal  eye?     This  condition  is  called  near-sightedness,  or  myopia. 

(7)  In  case  (5,  b),  if  a  subject  can  read  all  of  the  letters  expected 

of  the  normal  eye  one  credits  him  with  V=-,  but  the  eye  may  have 

accomplished  the  result  at  the  expense  of  more  or  less  effort. 

If  the  eye  have  a  punctum  remotum  beyond  infinity — i.  e.,  if  the 
rays  of  light  from  a  distant  object  are  not  yet  converged  to  a  focus 
by  the  time  they  reach  the  retina  in  the  resting  eye — it  will  require 
a  certain  effort  of  accommodation  to  produce  a  clear  image.  Such 
is  the  condition  in  the  far-sighted  person;  the  condition  is  called 
hyperopia.  The  term  far-sightedness  does  not  mean  that  the  subject 
can  see  farther  than  the  average  individual,  but  that  he  can  see  far 
objects  more  easily  than  he  can  see  near  objects.     If  a  subject  with 

F=-   can  see  as  clearly  or  more  clearly  when  the  +0.75  D.  lens  is 

in  front  of  the  eye,  there  is  no  reasonable  doubt  that  hyperopia  in 
some  form  is  present. 

(8)  Let  the  subject  direct  the  line  of  vision  toward  the  center 
of  the  chart  for  testing  astigmatism.  It  is  probable  that  not  all  of 
the  radiating  lines  will  appear  equally  clear-cut  and  black,  for  most 
persons  have  a  small  degree  of  astigmatism.  If  the  lines  are  un- 
equally clear,  where  are  the  clearest  ones  located  ?  Do  they  describe 
a  diameter  across  the  circle?  If  so,  describe  the  location  of  the  clear 
diameter,  0  degrees  to  180  degrees  being  the  horizontal  diameter,  and 
90  degrees  to  90  degrees  the  vertical  one. 

(9)  (a)  If  the  subject  has  normal  vision  with  no  astigmatism 
or  normal  vision  despite  a  slight  stigmatism,  he  may  be  given  a  better 
conception  of  just  what  a  moderate  degree  of  stigmatism  is  by  putting 
a  +1  D.  cyl.  lens  before  his  eye;  or  a  rather  high  degree  of  simple 
astigmatism  by  trying  +2  D.  cyl.  or  +3  D.  cyl. 

(b)  How  may  the  subject  be  made  artificially  hyperopic? 

(c)  How  artificially  myopic? 

(II)  To  Test  the  Color  Sense.  Let  the  subject  take  the  three 
test  colors — light  green,  purple,  and  red — and  choose  from  the  mass 
of  worsteds  the  colors  which  he  considers  similar  ones,  placing  the 
chosen  color  in  the  class  to  which  it  belongs.  It  is  not  difficult  to 
determine  whether  or  not  the  subject  has  a  defective  color  sense. 
If,  for  example,  he  is  red  blind  he  will  not  see  the  red  in  the  purple, 
or  related  colors,  but  will  classify  these  with  the  l)lues,  while  the 
reds  will  be  confused  with  the  greens. 


200  SPECIAL  PHYSIOLOGY 

X.    THE  RANGE  OF  ACCOMMODATION. 

The  amount  of  refractive  change  produced  by  the  eye  in  adjusting 
for  its  punctum  proximum  after  it  has  been  at  rest — i.  e.,  after  it 
has  been  adjusted  for  its  punctum  remotum — is  termed  the  range  of 
accommodation.  In  a  previous  chapter  the  functum  proximum  and 
punctum  remotum  were  determined.  It  was  reserved  for  this  place 
to  express  the  position  of  these  hmits  of  accommodation  in  terms 
of  dioptres,  and  thus  most  readily  determine  and  definitely  express 
the  range  in  simple  dioptres.  The  relation  of  this  to  what  has  just 
preceded  will  be  evident. 

Let  r  equal  the  punctum  remotum  expressed  in  dioptres — e.  g.,  if 
the  punctum  remotum  is  located  at  infinity  that  would  represent 
zero  dioptres  (r=0);  if  the  punctum  remotum  is  located  ^  m.  distant 
from  the  eye  r  would  equal  2  D. 

Let  p  equal  the  punctum  proximum  expressed  in  dioptres — e.  g., 
if  the  punctum  proximum  is  located  at  10  cm.  (^o  ^^•)  V  =  10  D. 

Let  a  equal  the  range  of  accommodation  in  dioptres;  then  a=p — r. 

To  apply  this  formula  to  the  above  example  we  have 
a^lOD— 2D  =  8D. 

1.  Experiments  and  Observations.  (1)  Determine  the  range  of 
accommodation  for  each  member  of  the  class. 

(a)  Determine  the  punctum  remotum  and  punctum  proximum. 
(h)  Record  these  quantities  in  metres. 

(c)  Substitute  these  values  in  formula  (5),  expressing  the  distances 
in  the  corresponding  dioptres — i.  e.,  using  the  reciprocals  of  the 
distances. 

(2)  Range  of  Accommodation  in  Myopia,  (a)  Is  r  positive  or 
negative  in  myopia? 

(b)  Is  a  always  less  than  p,  or  may  it  sometimes  be  greater? 

(c)  What  is  the  average  range  of  accommodation  of  the  myopes 
of  the  class? 

(3)  Range  of  Accommodation  for  Emmetropia.  (a)  What  is  the 
value  of  r  in  emmetropia? 

(6)  What  is  the  relative  value  of  a  and  p  in  this  class  of  cases  ? 

(c)  What  proportion  of  emmetropes  in  the  class? 

(d)  Have  they  all  the  same  range  of  accommodation? 

(e)  Can  any  probable  cause  be  assigned  for  any  variations  which 
may  be  found? 

(/)  How  does  the  average  range  for  emmetropes  compare  with 
the  average  range  for  myopes? 

(4)  Range  of  Accommodation  for  Hyperopia,  (a)  If  the  punctum 
remotum  is  ''beyond  infinity"  (!),  that  is  equivalent  to  saying  that  the 
eye  when  at  rest  does  not  focus  parallel  lines  (from  infinity)  upon  the 
retina,  but  the  lines  must  be  more  than  parallel — i.  e.,  from  beyond 


VISION  201 

infinity;  or,. better,  convergent;  but  if  they  are  convergent  they  would 
meet  behind  the  cornea.  The  punctum  remotum  for  hyperopes  is  then 
negative  in  direction  and  is  equal  to  the  distance,  behind  the  cornea,  at 

which  the  convergent  lines  would  meet  if  prolonged.     It  follows  that  - 

is  in  the  case  of  hyperopes  negative.  Our  formula  would  then  take 
the  form: 

a  ^  p  —  ( —  r),  or 
a  =  p  -{-  r. 

Now,  in  determining  r  one  may  use  a  convex  lens  of  such  strength 
as  to  give  the  rays  the  requisite  convergence.  The  value  of  the  lens 
in  dioptres  is,  of  course,  the  value  of  r.  In  the  hyperope  a  is  always 
greater  than  p.  As  the  determination  of  the  punctum  remotum  of 
the  hyperopic  eye  is  a  matter  for  the  clinician  to  deal  with,  we  will 
omit  its  determination  here. 

(6)  If  a  member  of  the  class  wears  glasses  having  the  following 
formula  for  the  right  eye,  +2  D.,  and  if  his  punctum  proximum  is 
12.5  cm.  distant  from  the  cornea,  what  is  his  range  of  accommodation? 

(c)  What  is  the  range  of  accommodation  for  those  hyperopes  in 
the  class  whose  punctum  remotum  may  be  determined  from  the 
lenses  wdiich  they  use? 

{d)  May  variations  in  range  be  accounted  for? 

(e)  Is  the  average  range  greater  or  less  than  that  for  myopes? 
For  emmetropes? 

(5)  Tabulate  the  values  of  p  and  of  r  for  the  class;  first,  with 
respect  to  age,  arranging  in  the  first  column  all  of  the  cases  which 
range  between  eighteen  and  twenty  years;  in  the  second  column 
twenty-one  to  twenty-three,  and  so  on.  Determine  the  average  for 
p  and  for  r  from  each  age  column. 

(a)  Does  age  within  the  limits  of  your  table  affect  the  punctum 
proximum?     If  so,  how? 

(b)  Does  age  affect  the  punctum  remotum  as  shown  by  your  table? 

(c)  If  the  volume  of  data  justifies  it,  make  a  chart  showing  the 
effect  of  age  upon  the  range  of  accommodation.  Use  the  values  of 
p  and  r  for  the  divisions  of  the  axis  of  ordinates. 


XI.    NORMAL  OPHTHALMOSCOPY   (DIRECT  METHOD). 

Gould  defines  ophthalmoscopy  as  "the  examination  of  the  interior 
of  the  eye  by  means  of  the  ophthalmoscope."  Normal  ophthal- 
moscopy is  the  examination,  by  means  of  the  same  instiMinciit,  of 
the  normal  eye  or  a  model  of  the  normal  eye. 

1.  Appliances.  An  ophthalmoscope,  with  concave  mirror;  diirk- 
room  huiijj,  and  Tlioringtori's  skiuscopic  eye  or  an  e(juivalent. 


202  SPECIAL  PH YSIOL OGY 

2.  Preparation.  Arrange  the  model  and  the  lamp  so  that  they 
will  be  in  the  horizontal  plane  with  the  observer's  eye.  Place  the 
skiascopic  eye  directly  in  front  of  the  observer's  eye,  and  the  lamp 
a  little  to  one  side  of  the  model. 

3.  Operation.  Let  the  observer  hold  the  ophthalmoscope  with 
the  right  hand,  mirror  forward,  close  to  the  eye,  directing  the  vision 
through  the  hole  in  the  instrument.  Throw  the  light,  reflected  by  the 
mirror,  into  the  skiascopic  eye.  Find  the  red  reflection  of  the  fundus, 
then  gradually  lessen  the  distance  between  the  observer's  eye  and 
the  model  to  about  2  cm.  or  3  cm.  The  skiascopic  eye  will  then  be 
illuminated  and  the  fundus  with  its  structures  will  be  clearly  defined. 

4.  Observations,  (a)  Adjust  the  Model  to  Represent  the  Emme- 
tropic Eye.  (1)  Determine  with  the  ophthalmoscope  the  color  of  the 
fundus.     Enumerate  the  structures  seen. 

(2)  Describe  the  papilla,  or  entrance  of  the  optic  nerve.  Is  the 
papilla  in  the  visual  axis  or  to  one  side  of  it?    Describe  its  position 

"with  respect  to  the  visual  axis  of  the  eye  and  determine  the  most 
advantageous  position  of  observer,  model  and  instrument,  to  get  a 
direct  view  of  the  papilla  in  the  right  eye;  in  the  left  eye. 

(3)  Describe  the  location  of  the  arteria  and  vena  centralis  retinoe 
with  reference  to  the  papilla. 

(4)  The  ring  formed  by  the  border  of  the  papilla  is  sometimes 
called  the  scleral  ring  or  the  choroidal  ring.  Can  this  ring  be  dis- 
tinctly seen? 

(5)  The  macula  lutea  and  the  ]ovea  centralis  are  the  most  sensitive 
portions  of  the  retina  and  are  in  a  direct  line  with  the  visual  axis 
of  the  eye. 

What  is  the  most  advantageous  position  of  model,  observer,  and 
instrument  in  order  to  get  a  direct  illumination  of  this  part  of  the 
fundus?    Describe  the  appearance  of  the  structures  in  question. 

(6)  Describe  the  retinal  bloodvessels  minutely,  drawing  a  map  of 
their  distribution. 

(6)  The  Observations  of  the  Retina  in  the  Hyperopic  Eye.  Adjust 
the  model  for  three  dioptrics  of  hyperopia. 

(7)  Are  the  retinal  bloodvessels  distinct  when  the  above-described 
method  of  observation  is  used? 

(8)  Place  in  a  rack,  before  the  model  eye,  the  following  lenses, 
with  each  one  testing  for  a  distinct  retinal  image: 

+  1  D.,   +2  D.,  +3  D.,  and  +4  D. 

With  which  one  of  the  lenses  is.  the  clearest  image  obtained  ?  Are 
all  of  the  figures  of  equal  size?    Explain,  giving  a  figure. 

(9)  In  hyperopia  do  the  rays  focus  in  front  of,  on,  or  behind  the 
retina?  What  direction  do  the  rays  take  after  leaving  the  hyperopic 
eye  from  the  illuminated  retina?  Are  they  parallel,  divergent,  or 
convergent  ? 


VISION  203 

(c)  Observation  of  the  Retina  in  a  Myopic  Eye.     Adjust  the  model 
for  myopia — e.g.,  three  dioptrics. 

(10)  Are  the  retinal  bloodvessels  distinct? 

(11)  What  direction  do  the  rays  from  the  retina  take  on  emerging 
from  the  myopic  eye:  divergent,  convergent,  or  parallel? 

(12)  In  which  of  these  three  cases  would  the  normal  eye  be  able 
to  get  a  clear  image  of  the  retinal  structures? 

(13)  In  which  case  would  a  correcting  lens  be  necessary?    Should 
one  use  a  convex  or  a  concave  lens,  and  why?^ 


XII.    NORMAL  OPHTHALMOSCOPY  (INDIRECT  METHOD). 

1.  Appliances.  The  same  as  in  preceding  exercise,  with  addition 
of  a  lens  of  ^  12  D.  to  +20  D. 

2.  Operation.  With  the  model  of  eye  to  be  observed,  the  light 
and  the  observer  arranged  as  above,  direct  the  light  reflected  by 
the  mirror  into  the  observed  eye  and  find  the  red  reflection  of  the 
fundus  of  the  eye.  Hold  the  lens  between  the  thumb  and  index  finger 
and  place  it  directly  between  the  mirror  and  the  eye  under  examina- 
tion, and  at  a  distance  from  the  latter  of  6  cm.  to  8  cm.  Be  careful 
that  the  center  of  the  lens  corresponds  to  the  center  of  the  pupil 
and  that  the  plane  of  the  lens  is  perpendicular  to  the  line  of  vision. 

3.  Observations,  (a)  Observations  of  the  Emmetropic  Eye.  (1) 
The  rays  of  light  emerging  from  the  observed  eye  are  focused  by  the 
convex  lens,  which  the  observer  holds,  and  forms  an  aerial  image  of 
the  retina.  If  a  +12  D.  lens  be  used,  and  if  its  optical  center  be 
held  8  cm.  from  the  anterior  surface  of  the  cornea,  how  far  from  the 
cornea  will  the  aerial  image  be  formed? 

(2)  Trace  in  the  image  all  of  the  structures  enumerated  in  the 
direct  method.  Is  the  image  erect  or  inverted?  Is  the  field  larger 
or  smaller  than  one  sees  in  the  direct  method?  Are  the  structures 
magnified  or  the  reverse?  Account  for  all  phenomena  representing 
the  optics  of  the  case  with  a  figure. 

(3)  Does  a  change  in  the  distance  between  the  cornea  of  the  model 
or  eye  and  the  lens  which  the  ol)server  holds  alter  the  size  of  the 
image?     Account  for  observation. 

(h)  Observation  of  the  Hyperopic  Eye.  Adjust  the  model  for  3  D. 
of  hyperojMa. 

C4j  Does  an  increase  of  tiie  distance  of  the  lens  from  the  cornea 
cause  the  image  of  the  papilla  to  be  altered  in  size?  Account  for  all 
phenomena. 

I  In  all  work  with  the  oplitliiiliiioHcopc  or  rotiiioMcopo  it  in  iiiKlcrHtood  (lial  tlic  oli.HCivt'r's 
cy<;  Ih  emmetropic,  eitlir-r  by  nature  or  by  eorreetioii,  and  that  Ium  aceomiiiodulioii  i»  hus- 
peiidetJ.  One  may  get  a  clear  view  of  the  retina  without  fulfilling  theHc  con<litionH,  but  one 
cannot  draw  reliable  o)>tical  conclnHionH. 


204  SPECIAL  PHYSIOLOGY 

(c)  Observation  of  the  Myopic  Eye.  Adjust  the  model  to  represent 
3  D.  of  myopia. 

(5)  Does  the  increase  of  the  distance  of  the  lens  from  the  eye  cause 
the  image  of  the  papilla  to  become  altered  in  size  or  reversed  in  posi- 
tion?   Account  for  all  phenomena. 

(6)  If  the  position  of  the  + 12  D.  lens,  which  the  observer  holds, 
remains  the  same — 8  cm.  from  cornea — will  there  be  any  variation 
in  the  distance  from  the  cornea  of  the  retinal  image  for  the  hyperopic 
eye  and  myopic  eye?  Will  the  distance  of  the  hyperopic  eye  be 
greater  or  less  than  for  the  emmetropic  eye?    Why? 

(d)  Observation  of  the  Human  Eye.  At  this  point  of  the  student's 
work,  let  him  practice  the  direct  and  indirect  method  of  ophthalmos- 
copy upon  his  comrades;  after  two  or  three  days  of  practice  he  may 
pass  to  the  following  exercise. 

XIII.  SKIASCOPY. 

Gould  defines  skiascopy  as  "a  method  of  estimating  the  refraction 
of  the  eye  by  observation,  through  ophthalmoscopic  mirror,  of  the 
movements  of  the  retinal  images  and  shadows."  Synonyms:  Fundus 
reflex  test;  umbrascopy;  pupiloscopy;  koroscopy;  kertoscopy;  retin- 
oscopy,  etc. 

1.  Appliances.  A  simple  retinoscope  or  an  ophthalmoscope 
with  a  plane  mirror;  Thorington's  skiascopic  eye  or  an  equivalent; 
dark-room  lamp,  etc. 

2.  Operation.  The  observed  eye  and  lamp  are  to  have  the  same 
relative  position  as  in  ophthalmoscopy.  Let  the  observer  sit  directly 
in  front  with  the  eye  in  the  same  horizontal  plane  with  the  lamp  and 
observed  eye,  and  somewhat  more  than  1  m.  distant  from  the  observed 
eye.  Throw  the  light  reflected  by  the  mirror  into  the  observed  eye; 
rotate  the  mirror  slowly  and  a  shadow  will  be  seen  in  the  pupil  of  the 
observed  eye. 

3.  Observations,  (a)  Observation  of  the  Emmetropic  Eye.  Adjust 
the  model  to  represent  emmetropia. 

(1)  Does  the  shadow  move  in  the  same  direction  as  the  mirror 
rotates  or  in  the  opposite  direction — i.  e.,  does  the  shadow  move  with 
the  mirror  or  opposite  f 

(2)  Is  the  movement  of  the  shadow  quick  or  slow? 

(b)  Observation  of  the  Myopic  Eye.  (I)  Adjust  the  model  to  represent 
less  than  1  D.  of  myopia. 

(3)  Note  that  the  shadow  movement  is  with  the  direction  of  the 
mirror  rotation,  and  that  it  is  relatively  quick. 

(II)  Adjust  the  model  to  represent  a  myopia  of   more  than  1  D. 

(4)  Note  that  the  shadow  movement  is  opposite  the  direction  of 
the  mirror  rotation,  and  that  it  is  quick  when  the  myopia  is  of  low 
degree;  slow  when  of  high  degree. 


VISION  205 

(5)  Observe  alternately  the  three  conditions  indicated  above  until 
their  differences  are  so  familiar  that  any  one  of  the  conditions 
may  be  readily  and  unerringly  detected  by  the  observer  when  they 
are  arranged  for  him  ))y  the  instructor. 

(c)  Observation  of  the  Hyperopic  Eye.  Adjust  the  model  to  repre- 
sent any  degree  of  hyperopia. 

(6)  Note  that  for  a  low  degree  of  hyperopia  the  shadow  movement 
is  ivith  the  mirror  rotation  and  quick. 

(7)  Note  that  for  higher  degrees  of  the  condition  the  shadow  move- 
ment is  with  the  mirror  and  slow. 

(S)  How  may  one  differentiate  a  high  degree  of  myopia  from  a  high 
degree  of  hyperopia? 

(9)  Is  there  any  difference  in  the  size,  shape,  distance,  or  position 
of  the  shadows  in  these  two  conditions? 

(d)  Observation  of  the  Human  Eye.  Let  the  student  practice  upon 
his  comrades.^ 

1  Observation  of  the  astigmatic  eye  is  intentionally  omitted  here.     It   belongs  more  espe- 
cially to  the  clinical  phase  of  the  subject. 


CHAPTER   VIII. 
THE  PHYSIOLOGY  OF  THE  NERVOUS  SYSTEM. 

I.  REFLEX  ACTION. 

1.  Material  and  Appliances.  Three  large,  vigorous  frogs;  operat- 
ing case;  sulphuric  acid,  0.5  per  cent.;  acetic  acid,  50  per  cent.;  dis- 
tilled water;  cork  board,  10  cm.  square;  hand  basin;  filter  paper; 
six  watch-glasses. 

2.  Preparation.  Pith  two  of  the  frogs,  taking  care  to  sever  the 
medulla  completely;  destroy  the  brain  but  leave  the  spinal  cord  intact. 
If  there  is  hemorrhage  plug  the  puncture  with  absorbent  cotton. 
Lay  the  pithed  frogs  ventrum  down,  with  legs  extended,  upon  a 
moist  paper.  Note  that  if  the  toes  be  pinched  the  leg  will  not  be 
flexed.  There  is  no  reflex  response.  The  animal  is  under  the  in- 
fluence of  shock.  This  condition  will  probably  last  for  half  an  hour 
or  more.  Recovery  will  be  indicated  by  the  drawing  up  of  the  legs, 
first  one  leg  and  then  the  other  being  flexed. 

3.  Observations,  a.  Modifications  of  General  Functions  by  Pithing. 
(1)  The  pithed  frogs  lie  upon  the  ventrum  with  legs  flexed.  The 
position  simulates  the  normal.  Make  a  detailed  comparison  of 
the  posture  of  the  pithed  frogs  with  that  of  the  normal  frog  under 
the  bell-jar. 

(2)  Compare  pithed  frogs  with  normal  as  to  the  appearance  of  the 
eyes. 

(3)  Study  the  respiratory  function  of  the  pithed  frogs. 

(4)  Is  the  heart,  as  observed  through  the  body  wall,  acting  with 
usual  rate  and  force  in  the  pithed  frogs? 

(5)  Gently  lower  a  pithed  frog  into  a  basin  of  cold  water.  Is 
there  an  adaptation  to  the  conditions?  Does  the  frog  swim?  Vary 
the  experiment  by  dropping  the  frog  from  a  height  of  six  inches. 
Take  a  yard  of  cord  and  tie  one  end  around  the  brachium  of  the 
normal  frog.  Repeat  the  experiments  with  the  normal  frog  and 
note  the  character  of  response. 

(6)  Place  a  pithed  frog  upon  a  cork  board;  gently  tip  the  board 
in  any  direction,  noting  whether  there  is  adaptation  in  equilibration. 
Repeat  the  experiment  with  the  normal  frog.    Describe  differences. 

(7)  Lay  a  pithed  frog  on  its  back  on  the  table;  will  it  right  itself? 
Try  a  normal  frog. 


THE  PHYSIOLOGY  OF  THE  NERVOUS  SYSTEM  207 

h.  Reflex  Response  to  Various  Stimuli.  Suspend  a  pithed  frog  by 
a  hook  through  its  mancHble.  The  body  and  legs  should  hang  freely, 
and  should  be  several  inches  from  the  table. 

(8)  ^Mechanical  Stimuli.  With  forceps  pinch  one  of  the  toes 
(not  the  longest)  of  the  hind  leg.  Pinch  the  skin  of  the  flank.  Pinch 
the  folds  of  skin  about  the  anus.  Note  response  when  stimulus 
is  varied  in  strength  and  applied  to  either  side. 

(9)  Thermal  Stimuli.  With  a  hot  wire  touch  the  skin  at  several 
points,  noting  response. 

(10)  Electric  Stimuli.  With  single-induction  shocks  stimulate 
skin  of  legs,  thighs,  or  flank,  using  fine  platinum- wire  electrodes,  and 
touching  the  moist  skin. 

If  single  shocks  elicit  no  response,  use  a  rapid  succession  of  shocks 
produced  by  bringing  the  Neef  hammer  into  the  primary  circuit. 

(11)  Chemical  Stimuli.  Cut  some  pieces  of  filter  paper  not  over 
2  mm  square.  Dip  a  piece  into  50  per  cent,  acetic  acid,  taking  care 
that  the  paper  is  saturated  and  that  there  is  no  excess  of  the  acid. 

Apply  the  acid  paper  in  turn  to  the  web  of  the  foot;  to  the  flank; 
to  the  ventrum;  median  line;  to  the  anus.  Note  the  character  of 
the  response,  as  to  extent,  single-sided  or  double-sided.  After  each 
application  of  acid  to  the  skin  of  the  frog,  the  acid  should  be  thor- 
oughly rinsed  or  swabbed  away. 

c.  The  Characteristics  of  Reflex  Response.  (12)  Purposive  Char- 
acter OF  Response.  In  the  responses  already  studied  the  observer 
could  easily  note  that  the  movements  possessed  the  manifest  pur- 
pose of  removing  the  offending  object.  In  many  cases  the  move- 
ments involved  several  sets  of  muscles,  but  in  every  case  all  the 
muscles  involved  in  the  response  acted  with  perfect  co-ordination, 
and  the  movement  was  well  directed  toward  the  removal  of  the 
irritation.    This  is  what  is  meant  by  the  purposive  character. 

In  order  further  to  illustrate  this  characteristic  of  response,  repeat 
Foster's  instructive  experiment:  "Choosing  a  strong  frog  in  which 
reflex  action  has  been  found  to  be  highly  developed;  suspend  it;  hold 
the  right  leg  firmly  down,  and  apply  a  square  of  acid  paper  to  the 
right  flank.  Twitchings  and  convulsive  movements  of  the  right  leg 
are  at  first  witnessed;  then  the  left  leg  is  brought  up  to  rub  the  right 
flank."     (Handbook  for  the  Phjj.sioloc/ical  Lahoraiory,  p.  409.) 

(13)  The  Latent  Period  of  Keflex  Response.  The  observer 
will  remember  that  in  most  of  the  above  experiments  the  responses 
did  not  follow  instantaneously  upon  the  application  of  the  stimulus; 
this  was  especially  i)oticeable  in  the  case  of  one  of  the  weaker  stimuli. 

In  order  further  to  illustrate  this  characteristic,  prepare  five  dilu- 
tions of  sulphuric  acid  in  as  many  watch-glasses;  hold  a  glass  so  that 
the  tip  of  the  longest  toe  ju.st  dips  into  the  acid.  Note  the  time 
rerjuired  to  elicit  a  resi)onse.  After  each  response  rinse  off  the  j)art 
.stimulated    and    allow  the   animal  to  rest    several    minutes,  testing 


208  SPECIAL  PHYSIOLOGY 

other  pithed  frogs  in  the  mean  time.  The  number  of  seconds  re- 
quired for  response  may  be  counted  from  a  metronome  or  from  a 
watch. 

Latent  periods  in  seconds. 

Strength  of  stinaulus.  , * , 

Frog  A.  Frog  B. 


H2S04 

0.05 

per  cent.  . 

H2S0, 

0.1 

li      (( 

H2S0, 

0.2 

It         u 

Hi,S04 

0.3 

<(       (( 

H2SO, 

0.4 

((        (. 

(14)  The  Irradiation  of  Reflex  Action.  In  the  above- 
described  experiment  it  will  probably  have  been  noted  that  the 
stronger  the  stimulus  the  more  extended  the  response — i.  e.,  the 
greater  the  number  of  muscles  brought  into  action. 

When  only  the  tip  of  the  toe  is  touched  to  very  weak  acid  the 
response  will  be  a  simple  flexion  of  the  tarsus,  and  this  only  after 
several  seconds.  When  stronger  acid  is  applied  to  the  toe  or  web 
the  crus  and  the  femur  may  both  be  flexed,  and  the  action  is  some- 
times repeated. 

Repeat  some  of  the  experiments,  paying  special  attention  to  the 
variation  of  extent  of  response,  with  varying  strength  of  stimulus. 

Note  that  in  some  cases  the  response  involves  the  opposite  side, 
as  well  as  higher  and  lower  levels  of  the  cord. 

(15)  Location  of  Reflex  Centers.  Take  one  of  the  pithed 
frogs  that  has  been  responding  typically.  Run  a  pithing  probe  down 
the  spinal  canal,  thus  functionally  destroying  the  spinal  cord. 

Apply  any  of  the  stimuli  mentioned  above.  Note  results,  and 
account  for  same. 


II.  REFLEXES  IN  THE  HUMAN  SUBJECT. 

Until  one's  attention  is  called  to  it,  he  is  likely  to  overlook  the 
great  importance  of  reflex  action  and  the  reflexes  in  the  mainte- 
nance of  the  human  body.  The  eyes  are  protected  from  dust  and 
other  irritable  substances,  the  lungs  from  dust  and  irrespirable 
gases,  through  the  intervention  of  reflex  action.  The  food  is  moist- 
ened and  the  digestive  juices  started  through  reflex  response  to  the 
stimulating  influence  of  food  in  the  mouth  and  digestive  canal.  The 
respiration,  circulation,  heat  regulation,  excretion,  and  various  other 
vital  processes  are  controlled  through  reflexes.  The  paramount  im- 
portance of  reflex  action  thus  becomes  apparent. 

A  disturbance  of  certain  reflexes  becomes  a  clinical  symptom  of 
considerable  importance. 

It  is  proposed  here  to  study  briefly  a  few  of  these  reflexes.  Their 
detailed  discussion  is  left  to  the  text-books. 


THE  PH rsiOL OGY  OF  THE  NER  VO US  S YSTEM  209 

1.  Appliances.  Glass  rod,  20  cm.  long,  with  rounded  ends; 
3  per  cent,  carbolic  acid;  beaker  of  water;  towel;  bristle  mounted 
in  handle. 

2.  Observations,  (a)  Respiratory  Reflexes.  (1)  Make  a  bristle 
aseptic.  Let  one  member  of  the  group  act  as  subject.  Let  the  sub- 
ject close  his  eyes.  The  observer  should  introduce  the  bristle  very 
gently  through  the  nostril,  and,  as  far  as  possible,  up  the  nasal 
passage.    The  response  will  probably  be  in  the  form  of  a  sneeze. 

Accidental  introduction  of  irritating  substances  into  the  respiratory 
passages  below  the  glottis  causes  coughing. 

(2)  Make  a  bristle  aseptic  and  bend  it  into  a  semicircle.  Let 
the  subject  open  the  mouth  wide,  depress  the  tongue,  and  say  "Ah!" 
prolonging  the  sound  several  seconds.  Introduce  the  bristle  into 
the  mouth;  pass  it  over  the  tongue  without  touching  the  latter;  turn 
the  point  downward  back  of  the  tongue,  and  tickle  the  glottis.  A 
convulsive,  reflex  movement  of  the  larynx,  sometimes  accompanied 
by  a  cough,  will  result. 

(6)  Circulatory  Reflexes.  (3)  Posture  influences  the  circulation 
reflexly.  Let  the  subject  remain  sitting  quietly  while  the  pulse  is 
counted  through  a  minute.  Note  the  number.  Let  the  subject  lie 
on  the  back  upon  the  table.  After  he  has  rested  quietly  three  to 
five  minutes,  take  the  pulse  rate  again.  Let  the  subject  stand  and 
observe  the  rate  after  three  to  five  minutes. 

(4)  Respiration  influences  the  circulation  reflexly.  Let  the  sub- 
ject sit  breathing  at  the  rate  of  thirty  respirations  per  minute  for  two 
minutes.  Count  the  pulse  during  the  second  minute.  Let  the  sub- 
ject then  drop  to  ten  respirations  per  minute  for  three  minutes,  and 
then  slower,  if  possible,  during  the  fourth  minute,  when  the  pulse  is 
to  be  counted. 

(5)  Exercise  influences  the  circulation  reflexly.  This  has  already 
been  demonstrated.     (See  Circulation.) 

(c)  Secretory  Reflexes.  (6)  The  chewing  of  anything  like  paraflSn 
or  rubber  incites  reflexly  the  free  flow  of  saliva.  In  a  similar  way  the 
presence  of  food  in  the  stomach  and  intestines  stimulates  the  secre- 
tory activity  of  the  digestive  glands. 

(d)  Reflexes  of  Deglutition.  (7)  Let  the  subject  open  the  mouth. 
Introduce  the  aseptic  glass  rod  into  the  mouth  without  touching 
tongue  or  cheeks.  Gently  touch  the  uvula;  it  wifl  probably  rise. 
Touch  the  fauces,  and  observe  the  convulsive  swallowing  move- 
ment.    Sometimes  this  merges  into  a  gaggitig  movement. 

The  raising  of  the  uvula  is  part  of  a  normal  swallowing  act.  The 
resfjonse  of  the  fauces  may  be  a  part  of  an  act  of  swallowing,  or  of 
a  protective  act  (gagging),  according  to  the  conditions  of  the  stimu- 
lation. 

(e)  Visual  Reflexes.  (8)  Let  the  subject  direct  his  vision  toward 
some  distant  object.    Make  a  sudflen  movement  with  hand  or  a  book 

14 


210  SPECIAL  PHYSIOLOGY     • 

as  if  to  strike  the  subject  in  the  face.     Observe  the  winking  of  the 
eyeHds — another  protective  reflex. 

(9)  Let  the  subject  again  direct  his  vision  toward  a  distant  object; 
gently  touch  the  conjunctiva  of  the  eyeball  with  the  sterilized  round 
end  of  the  glass  rod.    The  convulsive  winking  is  a  protective  reflex. 

(10)  Let  the  subject  sit  near  a  window,  and,  looking  through  the 
window,  direct  his  vision  toward  some  object  not  more  than  twenty 
feet  away.  Suddenly  shade  the  eyes  of  the  subject  for  a  few  moments; 
then  remove  the  shade  and  observe  the  change  in  the  size  of  the 
pupil.  During  the  experiment  let  the  subject  maintain  the  same 
state  of  accommodation,  if  possible. 

(/)  Cutaneous  Reflexes.  (11)  Tickle  the  base  sole  of  the  foot.  The 
foot  will  be  involuntarily  withdrawn — the  plantar  reflex. 

(12)  Pinch  skin  of  neck.  The  pupil  will  dilate — the  ciliospinal 
reflex. 

There  are  various  other  cutaneous  reflexes,  such  as  the  cremas- 
teric, abdominal,  epigastric,  scapular,  and  gluteal. 

(g)  "Tendon  Reflexes."  These  phenomena  are  not  really  reflexes, 
though  they  have  been  called  that  for  a  very  long  time.  They  may 
be  studied  in  this  connection.  Let  the  student  give  reasons  why  the 
responses  to  the  stimuli  are  not  necessarily  reflexes. 

(13)  Ankle  Clonus.  Let  the  subject's  leg  be  supported  as  by 
resting  it  across  a  chair,  the  subject  being  seated.  Let  the  observer 
place  the  hand  upon  the  ball  of  the  foot  and  press  suddenly,  so  as 
to  put  the  tendo  Achillis  upon  the  stretch.  There  results  a  series 
of  clonic  contractions.  This  phenomenon  is  not  observed  in  a  healthy 
subject. 

(14)  "Patellar  Reflex"  or  Knee-jerk.  Let  the  subject  cross  the 
legs  in  a  posture  frequently  assumed  when  sitting.  Tap  the  tendon 
below  the  patella  with  the  edge  of  the  hand,  with  the  back  of  a  thin 
book,  or  with  a  percussion  hammer.  The  quadriceps  extensor  muscle 
will  be  suddenly  stretched  and  will  respond  with  a  quick  contrac- 
tion, which  will  throw  the  foot  forward  in  a  kicking  motion.  This 
phenomenon  is  present  in  health,  and  it  may  be  modified  in  disease. 

III.  THE  ACTION  OF  STRYCHNINE  UPON  THE  NERVOUS  SYSTEM. 

1.  Material.     One  dog;  two  frogs;  sulphate  of  strychnine. 

2.  Preparation.  Make  a  solution  of  sulphate  of  strychnine,  0.01 
grm.  to  10  c.c;  also  concentrated  solution,  0.2  grm.  to  10  c.c.  pithed 
frogs.  Do  not  fasten  the  dog  to  the  dog  board.  Set  up  electric 
apparatus  to  obtain  tetanizing  current. 

3.  Experiments  and  Observations.  (1)  Hypodermic  injection 
of  2  mg.  strychnine  per  kg.  of  the  dog.  This  dose  is  invariably  lethal,, 
even  with  early  antidotal  treatment. 


THE  PH YSIOL OGY  OF  THE  NEB VO  US  S YSTEM  211 

(a)  Record  the  condition  before  and  S}Tnptoms  as  they  arise  after 
exhibition  of  the  drug,  especially  with  reference  to: 
(I)  Muscular  activity.     Describe  convulsions. 
(II)  Respiration.     How  affected  by  reflexes. 

(III)  Circulation.     Rapidity  and  rhythm  of  heart. 

(IV)  If  death  occurs,  which  stops  sooner,  the  circulation  or 
respiration  ? 

(6)  Formulate  results. 

(2)  Ligate  thigh  of  frog,  except  sciatic  nerve,  at  junction  with 
body.  Sever  all  structures,  except  nerve  and  femur,  just  below 
ligature.  Separate  cut  surfaces  with  rubber  tissue  to  prevent  diffu- 
sion of  the  drug.  Turn  the  frog  over  and  make  a  median  abdominal 
incision.  Pressing  viscera  aside,  pick  up  the  sacral  plexus  of  nerves 
going  to  the  uninjured  leg.  The  sacral  plexuses  may  be  readily  recog- 
nized, lying  on  each  side  of  the  median  line.  Pass  a  thread  loosely 
around  the  nerves,  so  as  to  quickly  find  them  when  wanted.  Inject 
into  dorsal  lymph  space  0.0001  grm.  strychnine. 

(a)  ^Yhat  part  of  the  frog  is  reached  by  poison?  What  part  is 
protected  from  it?    Illustrate  by  diagram. 

(b)  Were  strychnine  a  convulsant  through  its  action  on  the  sen- 
sorium,  would  the  legs  be  equally  convulsed?  If  it  acted  on  the 
spinal  cord?  If  it  acted  on  the  motor  nerves?  If  it  acted  on  the 
muscles  directly? 

(c)  Are  both  legs  convulsed? 

(d)  To  what  parts  in  the  reflex  arc  have  you  limited  the  action  of 
the  strychnine? 

(3)  Using  as  a  guide  the  thread  formerly  passed  around  it,  pick 
up  the  sacral  plexus  and  sever  it  high  up. 

(a)  Does  this  strychnine  reach  the  motor  nerve  and  the  muscles 
of  the  uninjured  leg? 

(b)  If  strychnine  were  a  convulsant  through  its  action  on  either 
the  motor  nerves  or  the  muscles,  or  both,  would  the  uninjured  leg 
still  participate  in  the  convulsions? 

(c)  Demonstrate  that  muscles,  sciatic  nerve,  and  sacral  plexus 
below  the  point  at  which  it  was  severed  are  still  intact  by  stimulating 
distal  portions  of  the  latter. 

(d)  To  what  elements  of  the  reflex  arc  have  you  limited  the  pos- 
sible action  of  «;trychnine? 

("4)  Expose  the  heart  of  a  frog  and  ligate  the  aortte  at  the  base. 
Operation  as  follows: 

P>eely  expose  sternum  by  +  shaped  incision  and  laying  back  of 
flaps.  Remove  lower  half  of  sternum  with  scissors,  taking  care  not 
to  injure  vessel  in  abdominal  wall,  which  comes  just  to  the  tip  of 
sternum.  Freely  incise  exposed  pericardium,  l)ringirig  heart  into 
view.  Grasp  apex  of  heart  with  forceps,  taking  care  not  to  use  force 
enough  to  cut  through  ventricular  wall,  and  draw  heart  down  and 


212  SPECIAL  PHYSIOLOGY 

forward.  This  gives  ready  access  to  bulbus  arteriosus  and  aortse. 
With  an  aneurysm  needle  pass  fine  thread  around  latter,  taking  care 
iiot  to  injure  auricle,  and  ligate. 

With  scalpel  cut  through  occipito-atlantoid  membrane  from  side 
to  side,  and  bend  head  forward.  Remove  posterior  wall  of  upper 
end  of  spinal  canal  by  inserting  smaller  blade  of  strong  scissors  into 
spinal  canal  and  cutting,  taking  care  not  to  injure  cord.  Allow  a 
drop  of  the  concentrated  solution  of  strychnine  to  fall  directly  upon 
cord;  or  with  fine  hypodermic  needle  inserted  1.5  cm.  into  the  arach- 
noid space  inject  two  drops  of  the  solution. 

{a)  What  effect  has  ligation  of  the  aortse  on  the  circulation? 

(h)  Would  stoppage  of  the  circulation  prevent  the  drug  from 
reaching  the  peripheral  terminations  or  trunks  of  the  sensory  nerves  ? 
Motor  nerves?     Muscles? 

(c)  Where,  then,  must  strychnine  act  to  produce  the  observed  symp- 
toms? 

{d)  Would  cessation  of  the  circulation  delay  the  action  of  strychnine 
on  the  cord  by  slowing  the  rate  of  its  absorption  by  the  latter? 

(5)  After  observing  results  in  experiment  (4),  destroy  first  the 
upper,  then  the  lower,  portion  of  the  cord  by  passing  a  wire  down 
the  spinal  cord. 

(a)  How  does  destruction  of  the  upper  part  of  the  cord  affect  the 
convulsions  ? 

(h)  What  is  the  result  of  the  destruction  of  the  entire  cord? 

(c)  Do  the  results  agree  with  those  of  previous  experiments? 

Note.  Destruction  of  the  upper  part  of  the  cord  during  the 
preparation  of  the  animal  may  take  place;  if  so,  the  upper  limbs 
will  not  take  part  in  the  convulsions. 

(6)  Further  Observations  and  Comparisons,  (a)  Compare  the  gen- 
eral effects  of  strychnine  and  curare  in  the  dog. 

(&)  Compare  results  obtained  in  experiments  consisting  of  ligating 
the  thigh  of  a  frog,  except  the  sciatic  nerve,  and  injecting,  in  the  one 
case  strychnine,  in  the  other  curare. 


IV.  THE  ACTION  OF  CURARE  UPON  THE  NERVOUS  SYSTEM. 

1.  Materials.  One  dog;  two  frogs;  normal  saline  solution;  curare; 
dry  cells;  inductorium;  hand  electrodes. 

2.  Preparation.  Prepare  the  following  solution:  sodic  chloride, 
curare,  0.2  grm.  to  10  c.c,  in  acidulated  20  per  cent,  alcohol.  Pith 
frogs.  Do  not  fasten  the  dog  to  the  board,  but  simply  restrain 
him.  Set  up  electric  apparatus  so  as  to  obtain  single  induction 
shocks. 

3.  Experiments  and  Observations.  (1)  Give  a  hypodermic  injec- 
tion of  0.01  grm.  per  kg.  curare  to  the  dog. 


THE  PHYSIOLOGY  OF  THE  NERVOUS  SYSTEM  213 

(a)  Record  the  condition  of  the  dog^  just  before  and  every  ten 
minutes  after  injections  of  curare,  with  special  reference  to: 

(I)  ^Muscular  activity. 
(II)  Respiration,  number  and  depth. 

(III)  Circulation,  rate  and  rhythm  of  heart  beat. 

(IV)  Which  stops  sooner,  respiration  or  circulation? 

(b)  Formulate  the  total  effect  of  curare  upon  the  animal. 

(2)  Ligate  the  thigh  of  a  frog,  except  the  sciatic  nerve  near  the 
knee-joint.     Inject  into  the  dorsal  lymph  space  0.002  grm.  curare. 

(a)  What  elements  enter  into  the  formation  of  a  reflex  arc  f 

(b)  What  motor  phenomena  would  result  from  increased  irrita- 
bility of  any  part  of  the  reflex  arc? 

(c)  What  motor  phenomena  would  result  from  lessened  irritability 
or  destruction  of  any  element  in  the  reflex  arc? 

(d)  What  effect  has  the  ligature  of  the  thigh  on  the  distribution 
of  the  curare? 

(e)  How  do  the  reflex  arcs,  of  which  the  gastrocnemii  are  the  motor 
ends,  differ  with  regard  to  the  distribution  of  the  curare?  What 
part  of  the  reflex  arc  is  protected  from  curare  in  the  ligatured  limb  ? 

(/)  Describe  the  relative  reaction  of  the  gastrocnemii  to  stimuli 
(chemical,  mechanical,  electric)  applied  to  the  various  parts  of  the 
body  and  limbs. 

(g)  Is  the  sensorium  intact?    Is  it  reached  by  the  curare? 

(h)  Is  the  cord  intact?    Is  it  reached  by  curare? 

(3)  Expose  the  sciatic  nerves,  near  the  body,  in  the  frog,  used  in 
the  experiment.     Stimulate  them. 

(a)  What  elements  in  the  reflex  arc  enter  into  consideration  in 
this  experiment? 

(b)  Which  of  these  elements  are  exposed  to,  which  protected  from, 
the  poison? 

(c)  Are  both  sciatics  reached  by  curare? 

(d)  Is  there  a  difference  in  the  reaction  of  the  gastrocnemii  to  the 
stimuli  applied  to  the  sciatic  nerves? 

(e)  To  what  elements  of  the  reflex  arc  have  you  limited  the  possible 
action  of  the  curare? 

(/;  Have  you  proven  that  curare  does  not  affect  the  nerve  trunks? 

(4)  Expose  gastrocnemii  by  cutaneous  incision.  Stimulate  the 
muscles  directly. 

(a)  Is  there  a  difference  in  reaction  to  stimuli? 

(b)  If  a  muscle  in  a  poisoned  animal  reacts  to  direct  stimuli,  but 
not  to  indirect  stimuli,  though  the  nerve  fibres  be  proven  to  be  intact, 
on  what  element  in  the  reflex  arc  must  the  poison  act? 

•  On  <l<>n:  Voluntary  muHcle«  first  paralyzed,  tlH?n  semivoliuitary,  e.  <7.,  rcHplration.  Stu- 
dentH  have  rnaintain«-d  lif<i  for  forty  niiniites  by  artificial  respiration  after  respiratory 
paralysis,  the  heart's  action  being  normally  Mtrong  after  complete  respiratory  paralysis. 


214  SPECIAL  PHYSIOLOGY 

(c)  Why  should  you  not  use  curare  as  an  anaesthetic  if  the  poisoned 
animal  does  not  react  to  painful  stimuli? 

(5)  Make  two  muscle-nerve  preparations  as  described  on  page  48. 
Dip  the  nerve  of  one  and  the  muscle  of  the  other  into  curare  solution. 
The  parts  of  the  preparation  not  immersed  should  be  kept  moist  with 
normal  saline  solution.  After  several  minutes  mount  specimens  in 
the  myograph.     Stimulate  the  nerves  and  note: 

(a)  The  relative  reaction  of  the  gastrocnemii  to  indirect  stimu- 
lation. 

(h)  Does  this  bear  a  resemblance  to  any  previous  experiment? 
(c)  How  do  results  compare  with  those  of  previous  experiments? 

(6)  Stimulate  the  same  muscles  directly? 
(a)  Relative  reaction. 

(6)  Taking  this  in  connection  with  the  preceding  experiment, 
where  have  you  proven  that  curare  acts? 

(c)  How  do  experiments  (5)  and  (6)  compare  with  experiments 
(3)  and  (4)?^ 


V.  THE  ACTION  OF  VERATRIN  UPON  THE  NERVOUS  SYSTEM. 

1.  Materials.     Sulphate  of  veratrin;  one  dog;  three  frogs. 

2.  Preparation.  Prepare  a  solution  of  veratrin,  50  mg.  to  10  c.c. 
Pith  frogs.  Restrain  dog,  but  do  not  fasten  to  board.  Set  up  myo- 
graph and  induction  coil,  the  latter  arranged  for  single-induction 
shocks. 

3.  Experiments  and  Observations.  (1)  Give  subcutaneous  injec- 
tion of  1  mg.  per  kg.  veratrin  to  the  dog. 

(a)  Describe  symptoms  as  they  arise. 

(b)  Summarize. 

(2)  Place  thread  around  the  sacral  plexus  of  the  pithed  frog  so  as 
to  easily  find  it,  as  described  under  strychnine.  Inject  0.003  grm. 
veratrin  into  dorsal  lymph  space. 

(a)  Describe  symptoms  referable  to  reflexes. 
(h)  Note  particularly  the  difference  between  a  forcible  contraction 
and  a  prolonged  contraction. 

(3)  Sever  the  sacral  plexus  around  which  the  thread  has  been 
passed. 

'^  Failure  in  experiments  (5)  and  (6)  may  result  from  insufficient  immersion  of  muscle  in 
curare  solution,  capillary  attraction  resulting  in  the  curare  reaching  muscle  supposed  to  be 
free  from  poison,  and  drying  of  parts  not  immersed  in  solution.  Of  these  the  first  is  by  far 
the  most  frequent  cause  of  failure,  and  the  sheath  of  the  muscle  rendering  the  absorption  of 
poison  a  slow  process.  It  may  be  overcome  by  making  a  few  slight  incisions  in  sheath,  or 
injecting  a  drop  of  the  curare  solution  directly  into  the  muscle. 

The  immersed  nerve  preparation  often  fails  through  death  of  nerve. 

Failure  of  experiment  (2),  and  consequently  (3)  and  (4),  may  result  from  ligature  around 
thigh  being  not  tight  enough  to  prevent  diilusion  of  curare  into  gastrocnemius. 


THE  PR YSIOL OGY  OF  THE  NER  VO  US  S YSTEM  215 

(a)  How  do  contraction  of  the  legs  in  response  to  direct  stimuli 
compare  ? 

(6)  Has  severing  the  sacral  plexus  altered  the  duration  of  the  con- 
traction of  the  muscles  supplied? 

(c)  If  veratrin  still  produces  its  typical  effects,  to  what  elements 
in  the  reflex  arc  have  you  limited  its  action? 

{d)  Compare  the  effect  of  severing  the  sacral  plexus  in  a  frog 
poisoned  with  veratrin  with  that  of  a  frog  poisoned  with  strychnine. 

(4)  Ligate  the  thigh  of  a  pithed  frog  at  the  junction  with  \he  body, 
not  including  in  the  ligature  the  sciatic  nerve.  Sever  all  tissues  just 
below  the  ligature  except  the  nerve  and  the  femur.  Carefully  separate 
the  cut  surfaces  with  rubber  tissues  so  as  to  prevent  diffusion  of  the 
drug.     Inject  0.003  grm.  veratrin  into  the  dorsal  lymph  space. 

(a)  By  means  of  a  diagram  show  the  distribution  of  the  poison. 

(h)  Compare  the  contraction  of  the  legs,  noting  particularly  the 
difference  in  the  duration  rather  than  the  difference  in  the  force  of 
contraction. 

(c)  If  the  protected  limb  reacts  normally,  to  what  elements  in  the 
reflex  arc  have  you  limited  the  possible  action  of  veratrin. 

{d)  Compare  results  with  similar  experiment  with  strychnine. 

(5)  From  the  frog  used  in  experiment  (4)  make  two  gastrocnemii 
preparations.  Fasten  in  myograph  by  means  of  femurs  and  stimulate 
them  directly,  making  tracings  of  contractions. 

(a)  Compare  tracings. 

(6)  To  what  elements  have  we  limited  the  action  of  veratrin? 

(c)  Suggest  an  experiment  which  would  limit  the  action  to  one 
element. 

(6)  Very  cautiously  sniff  veratrin.    Describe  the  sensation. 

(7)  General  observations  and  comparisons. 

(a)  Review  your  notes  on  the  action  of  curare,  strychnine,  and 
veratrin  upon  the  reflex  arc. 

(h)  How  would  you  prove  that  a  drug  paralyzed  by  its  action  on 
the  spinal  cord? 

(c)  How  would  you  prove  that  a  drug  destroyed  reflex  activity  by 
its  action  on  some  part  of  the  sensorium? 


VI.   SENSATION. 

The  phenomena  of  reflex  action  and  the  function  of  the  several 
elements  of  the  reflex  arc  have  been  studied.  It  will  l)e  remembered 
by  the  subject  on  whom  were  observed  the  phenomena  of  human 
reflexes  that  he  was  conscious  of  all  the  stinndi,  though  he  was  un- 
conscious of  the  response  until  it  had  already  been  efl'ected. 

The  sensory  element  of  the  reflex  arc — the  dendritic  element  of 
the  aflerent  spinal  neuron — carries  from  the  perij)liery  to  the  spinal 


216  SPECIAL  PHYSIOLOGY 

cord  messages  or  impressions  of  stimuli.  There  is  no  conscious 
sensation  in  the  cord.  Motor  centers  in  the  cord  may  send  out 
impulses  to  muscles,  thus  producing  the  reflex  responses. 

If  the  brain  is  intact  the  impression  travels  through  the  cord  to 
the  sensorium,  where  it  becomes  a  sensation.  In  the  mean  time  the 
cord  may  have  returned  motor  impulses  of  reflex  action.  These 
motor  impulses  pass  away  from  the  central  nervous  system  and 
therefore  never  reach  the  sensorium — never  give  rise  to  sensations. 
The  efferent  reflex  impulses  cause  action  of  end-organs — e.  g., 
muscles.  One  is  unconscious  of  the  impulse,  but  he  is  conscious  of 
the  action  through  sensory  impressions  coming  to  the  brain  from  the 
organs  in  activity.  The  relation  between  sensation  and  reflex  action 
has  been  set  forth. 

The  relation  between  sensation  and  voluntary  action  is  somewhat 
less  direct.  When  an  animal  takes  food  into  the  digestive  tract  it 
is  in  response  to  the  sensation  of  hunger.  When  he  seeks  shelter  it 
is  in  response  to  sensations  of  uncomfortable  exposure.  These  are 
direct  voluntary  response  to  sensation. 

When  one  prepares  food  for  a  future  meal  or  builds  a  shelter,  he 
anticipates  the  coming  sensation  of  hunger  or  exposure  and  forestalls 
it.  Here  we  have  an  intervention  of  reason  or  of  instinct,  inducing  a 
series  of  voluntary  actions. 

Voluntary  action  is,  then,  either  directly  or  indirectly  dependent 
upon  sensation. 

Finally,  sensation  is  the  source  not  only  of  all  activity,  but  of  all 
knowledge.  Its  importance  in  any  study  of  the  nervous  system  then 
becomes  paramount. 

Besides  the  auto-objective  sensations — hunger,  thirst,  suffocation, 
fatigue,  pain,  shivering,  and  tickling — there  are  the  distinctively 
objective  sensations:  touch,  posture,  temperature,  smell,  taste,  hearing, 
and  vision. 

1.  Appliances.  Dividers;  millimetre  rule;  two  beakers;  two  20d 
spikes,  and  towel. 

2.  Observations,  a.  Tactile  Sensation.  (1)  To  test  the  acuteness 
of  the  tactile  sense  as  well  as  the  power  of  localization.  Take  a  pair 
of  dividers  whose  points  may  be  approximated  to  a  millimetre  or 
less.  Let  the  subject  of  the  observations  be  blindfolded.  Apply  the 
points  to  the  tip  of  the  ring  finger  so  as  to  bring  the  line  between 
the  two  points  transverse  to  the  axis  of  the  finger.  Press  the  points 
gently  and  draw  them  over  the  skin  for  a  distance  of  1  mm.  If  the 
subject  feels  two  points,  bring  them  nearer  together  and  repeat  the 
experiment;  presently  the  points  will  have  been  brought  so  near 
together  that  they  can  no  longer  be  distinguished  as  two,  but  the 
sensations  are  merged  into  one.  The  crucial  point  has  been  passed. 
The  greater  the  acuteness  of  tactile  sense,  the  nearer  the  points  may 
be  brought  together  and  yet  be  felt  as  two  points.    What  is  the  limit 


THE  PH YSIOL OGY  OF  THE  NEB VO US  S YSTEM  21 7 

of  acuteness — i.  e.,  how  near  together,  expressed  in  millimetres,  may 
the  points  be  felt  as  two? 

Place  the  dividers  upon  any  portion  of  the  subject's  hand  and 
test  the  acuteness  of  touch;  the  subject  will  be  able  to  describe  accu- 
rately where  the  points  touch  the  surface  and  the  more  accurately 
the  more  acute  the  tactile  sense  as  tested  in  the  above  manner. 

(2)  In  a  similar  way  test  the  acuteness  of  tactile  sensation  in  the 
following  locations: 

Left  fourth  finger — tip;  palmar  surface  of  third,  second,  and  first 
phalanges;  dorsal  surface  of  second  and  first  phalanges. 
Left  hand — mid-palm,  mid-back. 
Left  wrist — flexor  surface,  extensor  surface. 
Left  forearm — flexor  surface,  extensor  surface. 
Left  upper  arm — flexor  surface    extensor  surface. 
Left  scapular  region. 

(3)  Tabulate  results  for  left  and  right  side  in  case  of  Mr.  A. 

('4)  Tabulate  results  for  left  and  right  side  for  at  least  two  indi- 
viduals. 

(5)  Make  a  careful  study  of  the  results  with  a  view  to  answering 
the  following  questions,  which  answers  may  be  formulated  in  a 
series  of  conclusions: 

(a)  Do  different  parts  of  the  same  individual  possess  the  same 
acuteness  of  tactile  sensations? 

(h)  Do  symmetrically  located  points  in  the  same  individual  possess 
the  same  acuteness  of  tactile  sensation? 

(c)  Is  there  any  appreciable  variation  of  acuteness  of  tactile 
sensation  in  homologous  points  of  different  individuals? 

(d)  Is  there  any  difference  in  the  acuteness  of  tactile  sensation 
between  the  flexor  and  corresponding  extensor  surfaces? 

(e)  Is  there  a  progressive  decrease  of  acuteness  as  one  passes 
from  tip  of  finger  up  along  the  anterior  limb? 

(/)  Formulate  any  other  conclusions  which  may  be  based  upon  the 
observations. 

h.  The  Temperature  Sense.  (6)  Map  out  upon  the  flexor  surface 
of  the  forearm  a  3  cm.  square  field,  dividing  it  into  100  squares 
each  3  mm.  square.  Draw  a  similar  map  on  paper.  Fill  one  beaker 
with  chipped  ice  and  water,  and  another  with  water  at  60°  C.  Put 
a  spike  in  each  beaker. 

Wrap  the  cold  spike  in  a  towel  in  ortler  that  it  may  maintain  its 
temperature  as  long  as  possible.  Place  its  point  gently  on  one  of 
the  squares  of  the  skin  map;  if  it  feels  cold  to  the  subject  make  a 
"c"  in  the  corresponding  square  of  the  paper  map.  Slij)  the  cold 
point  from  scjuare  to  scjuare  of  the  skin,  noting  those  squares  which 
give  the  sensation  of  cold  and  recording  same  on  paper  map. 

(7)  After  finding  the  cold  areas,  determine  in  a  similar  manner 
the  areas  which  give  a  sensation  of  heat  for  the  warm  spike. 


218  SPECIAL  PHYSIOLOGY 

(8)  Test  blank  areas  to  determine  whether  their  tactile  sense  is 
more  acute  than  that  of  the  hot  and  cold  spots. 

(9)  Formulate  conclusions  in  answer  to  the  following  questions: 

(a)  Are  all  portions  of  the  skin  equally  sensitive  to  temperature 
change  ? 

(b)  Are  all  portions  of  the  skin  equally  sensitive  to  cold? 

(c)  Are  all  portions  of  the  skin  equally  sensitive  to  heat? 

{d)  What  percentage  of  the  space  in  the  skin  map  is  sensitive  to 
cold?    To  heat? 

(10)  Place  a  cold  coin  on  the  palm  of  the  hand;  the  same  coin  at 
same  temperature  on  the  back  of  the  hand. 

In  which  of  these  two  positions  does  the  coin  feel  the  larger? 
Why? 

VII.  SENSATION  (Continued). 

c.  The  Sense  of  Equilibrium.  Through  the  sense  of  equilibrium 
one  is  able  to  balance  the  body  when  sitting,  standing,  walking,  or 
riding.  In  order  to  study  some  of  the  phenomena  of  equilibration 
try  the  following  experiments: 

(1)  Apply  a  bandage  to  a  subject's  head  in  the  horizontal  plane. 
Slip  a  very  sharp  pencil  fa  pen  or  a  needle  will  answer),  point  up, 
behind  the  bandage  in  such  a  way  that  the  point  will  be  held  firmly 
upright  by  the  bandage  and  register  the  movements  of  the  head. 

Smoke  a  kymograph  drum;  after  the  drum  cools  slip  the  paper  off 
the  drum  without  cutting  it. 

Arrange  two  horizontal  arms,  adjustable  as  to  width  and  height, 
but  held  parallel  by  construction  of  apparatus.  Slip  the  cylinder  of 
carboned  paper  over  the  arms  and  separate  them  until  the  paper  is 
stretched  and  held  in  two  parallel  sheets  with  horizontal  surfaces 
above  and  below. 

Adjust  the  carboned  surfaces  so  that  when  the  subject  stands 
€rect  the  point  of  the  pencil  (pen  or  needle)  will  just  touch  the  lower 
surface. 

Let  the  subject  take  a  position  beneath  the  carboned  surface, 
standing  erect  and  as  still  as  possible.  Any  deviations  from  the  erect 
position  will  be  traced  upon  the  carboned  paper.  At  the  end  of 
one  minute  close  the  observation.  The  paper  bears  an  accurate 
record  of  the  equilibration  of  the  subject. 

(2)  Shift  the  paper  a  few  inches,  exposing  a  fresh  field.  Let  the 
•subject  again  take  position,  standing  as  still  as  possible  this  time 
with  closed  eyes.    The  observation  lasts  one  minute  as  before. 

(3)  Repeat  the  observation,  letting  the  subject  stand  upon  one  foot: 
(a)  with  eyes  open;  (6)  with  eyes  closed. 

(4)  Choose  another  subject  as  different  as  possible  from  the  first 
in  stature.    Compare  his  tracings  with  those  of  subject  number  one. 


THE  PHYSIOL OGY  OF  THE  XER  VO  US  S YSTEM  9 1  9 

fo)  How  many  elements  enter  into  the  more  or  less  complex 
perception  of  equilibrium?  Has  the  tactile  or  pressure  sense  of  the 
soles  of  the  feet  anything  to  do  with  it?  Has  the  muscular  sense 
or  sense  of  muscle  tension  any  part  to  play?  What  role  does  vision 
play?     Are  there  other  factors?     Formulate  conclusions. 

d.  The  Muscle  Sense.  This  might  better  be  called  the  sense  of 
muscle  tension.  It  enters  largely  into  the  maintenance  of  equilibrium. 
It  is  an  important  factor  in  all  voluntary  movements  because  through 
it  one  gauges  the  strength  of  motor  impulse  to  be  used  in  each 
movement. 

(6)  Take  two  wooden  cylinders  of  exactly  the  same  shape  and  size, 
but  differing  in  weight  Vjy  an  appreciable  amount.  Let  the  several 
members  of  the  group  weigh  the  cylinders  in  their  hands,  determin- 
ing which  is  the  heavier. 

(7)  Take  two  wooden  cylinders  alike  in  weight,  but  differing  in  size. 
I^et  the  members  of  the  group  test  them  and  describe  their  sensations. 
Account  for  the  sensation. 

e.  Gustatory  Sensation.     Prepare  the  following  solutions: 
(I)  10  grams  of  cane-sugar  in  1  litre  distilled  water. 

(H)   1  centigram  sulphate  of  quinine  in  1  litre  distilled  water. 
(HI)  1  gram  glacial  acetic  acid  in  1  litre  distilled  water. 
(IV)  10  grams  dry  sodium  chloride  in  1  litre  distilled  water. 

(8)  To  determine  the  acuteness  of  taste,  take  a  uniform  quantity  of 
the  solution  into  the  mouth  at  each  observation.  A  convenient 
quantity  is  4  c.c.  Rinse  the  mouth  with  distilled  water,  or  with 
boiled  water,  before  each  test. 

Any  person  with  normal  taste  is  able  to  detect  the  taste  of  the 
standard  solutions.  In  order  to  determine  how  much  weaker  the 
solution  may  be  and  yet  be  detected,  make  dilutions  of  the  standard 
solutions,  recording  the  final  results  in  number  of  parts  of  water  to 
one  of  the  substance  in  question. 

(9)  Tabulate  for  the  class  and  determine  average  strength  of  each 
solution  that  marks  limit  of  acuteness. 

(10)  Vary  the  experiments  by  modifying  temperature  of  solutions 
(10°,  20°,  30°,  and  40°  C).  Note  latent  period.  Note  whether  sub- 
jects habitually  use  tobacco. 

(11)  Formulate  a  series  of  conclusions  from  the  data  collected. 

(12)  To  determine  localization  of  sense  of  taste — i.  e.,  to  find 
whether  there  are  areas  of  the  gustatory  region  which  are  especially 
.sensitive  to  particular  stimuli;  bitter,  for  example. 

Through  the  aid  of  a  probang  apply  to  different  limited  areas  of 
the  tongue,  pahite,  fauces,  and  buccal  mucous  surface  either  the 
standard  solution  or  somewhat  stronger  solutions  of  the  same  sub- 
stances. 

Is  the  tip  of  the  tongue  equally  sensitive  to  the  four  different 
tastes?     The  edges?    Tlie  dorsum?    The  back? 


220  SPECIAL  PHYSIOLOGY 

(13)  Draw  a  map  of  the  tongue,  locating  those  areas  most  sensitive 
to  the  four  tastes,  severally. 

/.  Auditory  Sensation.  (14)  To  test  acuteness  of  hearing,  deter- 
mine how  far  the  subject  can  hear  a  watch  tick  when  the  timepiece 
is  held  at  the  level  of  the  head,  and  some  distance  to  one  side.  Record 
distance  in  centimetres. 

(15)  To  determine  the  highest  pitch  discernible  by  the  ear  test  the 
subject  with  a  Galton  whistle,  recording  the  number  of  vibrations  per 
second  audible. 

g.  Visual  Sensation.     (See  Chapter  on  Vision.) 

VIII.  FUNCTION  OF  SPINAL  NERVES. 

It  is  intended  here  simply  to  outline  a  technique  which  may  be 
used  in  making  tests  of  any  efferent  nerve  trunk. 

In  testing  a  spinal  nerve  trunk  one  has  the  choice  of  stimulating 
the  anterior  root — the  efferent  or  motor  root — or  of  stimulating  the 
whole  trunk.  If  one  stimulates  the  anterior  root  only  there  is  no 
need  of  cutting  the  nerve  root  next  to  the  cord,  as  all  impulses  are 
efferent. 

In  testing  a  nerve  trunk,  it  is,  however,  necessary  to  cut  the  nerve 
and  stimulate  the  distal  end  only,  if  one  wishes  to  observe  the  action 
of  the  motor  fibres.  If  the  trunk  were  not  cut,  some  of  the  fibres, 
being  afferent  and  sensory,  would  carry  impressions  to  the  cord  and 
elicit  a  reflex  response  which  would  seriously  complicate  the  obser- 
vation of  the  direct  efferent  impulses  from  the  point  of  stimulation 
to  the  motor  distribution  of  the  nerve.  Results  to  be  of  any  value, 
therefore,  must  be  gotten  through  the  electric  stimulation  of  distal 
ends  of  cut  nerve  trunks. 

1.  Appliances.  Dry  cell;  inductorium;  contact  key;  short-circuit- 
ing key;  three  wires;  shielded  electrodes  with  wires;  small  dog  or 
large  rabbit;  chloroform  or  ether;  clippers;  operating  case. 

2.  Preparation.  Fasten  animal  to  holder,  anaesthetize,  clip  the 
throat,  and  set  up  electric  apparatus  for  single-induction  shocks. 

3.  Operation.  Dissect  out  any  nerve  trunk  which  it  is  proposed 
to  test.  Take,  for  example,  one  of  the  several  trunks  of  the  brachial 
plexus;  take  the  fifth  cervical. 

Make  a  cutaneous  incision  along  the  outer  margin  of  the  sterno- 
cleidomastoid muscle.  Separate  the  subcutaneous  tissues  and  deeper 
tissues  to  expose  the  cervical  nerve  trunks  as  they  emerge  from  between 
the  scalene  muscles.  Identify  the  fifth  cervical  trunk  and  separate 
it  from  the  surrounding  tissues  suflficiently  to  permit  the  introduc- 
tion of  the  shielded  electrode  beneath  it.  Tie  a  ligature  around 
the  nerve  close  to  the  spinal  column  and  cut  the  nerve  beyond  the 
ligature. 


THE  PH YSIOL OGY  OF  THE  NEB VO  US  S YSTEM  221 

4.  Observation.  (1)  Lay  the  distal  end  of  the  cut-off  nerve  upon 
the  electrode.  Stimulate  with  single-induction  shocks  of  optimum 
strength.  Watch  carefully  the  response  of  the  muscles  and  repeat 
the  stimulus  until  the  movement  is  perfectly  understood.  What  is 
the  general  movement? 

(2)  Palpate  the  muscles  as  the  stimulation  is  repeated  and  deter- 
mine the  individual  muscles  which  respond. 

(3)  In  what  order  do  the  several  muscles  contract?  Is  the  move- 
ment due  to  a  single  muscle  or  to  several  acting  together? 

(4)  Vary  the  experiment  by  tetanizing  the  muscles.  Are  any  new 
facts  discovered? 

In  a  similar  way  any  nerve  trunk  may  be  stimulated  and  the 
response  studied. 


CHAPTER   IX. 
THE  PHYSIOLOGY  OF  THE  MUSCULAR  SYSTEM. 

The  physiology  of  contractile  tissues  was  treated  under  General 
Physiology.  This  chapter  should  follow  that,  and  presupposes  a 
knowledge  of  the  human  skeleton  and  skeletal  muscles. 

I.  ANIMAL  MECHANICS. 

Animal  mechanics  is  the  application  of  the  laws  of  mechanics  to 
animal  motion.  The  bones  are  used  as  levers;  the  articular  surfaces 
of  bones  usually  serve  as  fulcrums,  while  the  power  is  exerted  by 
the  muscles.  In  a  vast  majority  of  cases  the  bones  represent  levers 
of  the  third  class — in  which  rapidity  of  motion  is  attained  at  the 
expense  of  power.  In  other  words,  the  arrangement  of  the  bone- 
muscle  organs  is  such  that  a  contraction  of  a  muscle — moderate  in 
extent  and  rate  of  motion — is  manifested  by  a  movement  of  the  limb 
which  is  much  in  excess,  as  to  extent  and  rate,  of  the  movement  of 
the  power. 

In  solving  problems  in  animal  mechanics  the  principal  factors  ta 
be  considered  are:  (1)  The  relative  length  of  the  two  lever  arms; 
(2)  the  relative  size  of  the  muscles  involved  in  any  movement;  (3)  the 
direction  in  which  the  power  acts,  and  (4)  the  weight  to  be  moved. 

a.  Problems  in  Animal  Mechanics.  Two  typical  problems  in 
animal  mechanics  are  the  following: 

1.  Determine,  in  a  particular  case,  the  tension  exerted  upon  the 
tendo  Achillis  in  supporting  the  weight  (60  kilograms)  of  the  subject 
upon  the  ball  of  the  foot. 

2.  How  much  tension  was  there  on  the  biceps  tendon  in  the 
subject  upon  your  dissecting  table  when  he  held  a  10-kilo  iron  ball 
in  the  most  advantageous  position  ?  This  is  a  typical  problem  and 
its  solution  will  make  the  difficulties  to  be  encountered  apparent.  It 
will  also  show  that  nothing  more  than  an  approximate  solution  can 
be  attained  without  an  extended  and  detailed  study. 

Solution.  The  principal  muscle  involved  in  the  required  action 
being  the  biceps,  the  most  advantageous  position  is  the  one  in  which 
that  muscle  exerts  its  power  in  a  line  perpendicular  to  the  lever. 
Placing  the  subject's  arm  as  nearly  as  possible  in  that  position,  one 
takes  the  following  measurements:     (1)  The  long  arm  of  the  lever; 


THE  PHYSIOLOGY  OF  THE  MUSCULAR  SYSTEM 


223 


this  would  be  from  the  center  of  articulation  between  the  humerus 
and  the  ulna  to  the  center  of  the  10-kilo  ball,  which  would  be, 
approximately,  to  the  end  of  the  metacarpal  bone  (36  cm.). 

(2)  The  short  arm  of  the  biceps  lever;  this  would  be  the  distance 
from  the  center  of  the  insertion  of  the  biceps  to  the  fulcrum — the 
center  of  articulation  (6  cm.). 

(3)  The  short  arm  of  the  lever  for  the  brachialis  anticus.  If  the 
brachialis  anticus  were  exactly  parallel  to  the  biceps  the  short  arm 
would  be  the  distance  from  the  insertion  to  the  fulcrum  (5  cm.),  as 
in  the  biceps;  but  it  is  not  parallel.  A  hne  drawn  from  the  fulcrum 
perpendicular  to  the  axis  of  the  brachialis  anticus  /  a'  is  shorter 
than  the  line  fa.  The  angle  between  the  brachialis  anticus  and  the 
biceps  is  approximately  10  degrees;  therefore  the  angle  a'  j  a  would 
be  approximately  10  degrees;  then  a'  f  is  the  cosine  10  degrees,  or 
98  per  cent,  of  the  radius  a  f  (5  cm.),  or  4.9  cm.  (Fig.  84). 


Mechanics  of  flexion  of  the  forearm.     (The  upper  a  is  to  be  understood  as  a'.) 


(4)  The  power  arm  of  the  supinator  longus  is  the  perpendicular 
distance  from  the  fulcrum  to  the  line  of  force  of  the  supinator  longus, 
and  is  represented  by  the  line  /  s,  which  is  4.8  cm.  Now  the  carpal 
and  digital  flexors  which  take  origin  from  the  humerus  act  as  forearm 
flexors  after  having  flexed  the  carpus  and  digits.  In  the  action  under 
consideration  they  would  not  be  brought  into  forcible  action  as 
carpal  and  digital  flexors.  We  may,  therefore,  ignore  them  and 
confine  our  discussion  to  the  three  muscles  mentioned  above. 

In  the  action  of  the  biceps  the  long  arm  is  36  cm.  and  the  short 
arm  6  cm.;  in  the  action  of  the  brachialis  anticus  the  long  arm  is 
36  cm,  and  the  short  arm  4.9  cm.;  in  the  action  of  the  supinator 


224  SPECIAL  PHYSIOLOGY 

longus  the  long  arm  is  36  cm.  and  the  short  arm  4.8  cm.  Reducing 
these  to  per  cent,  ratios  we  have:  For  the  biceps,  which  we  will 
designate  as  h,  16.6  per  cent,  leverage;  for  the  brachialis  anticus, 
which  we  will  designate  as  a,  13.6  per  cent,  leverage;  and  for  the 
supinator  longus,  which  we  will  designate  as  s,  13.3  per  cent,  leverage. 

But  there  is  another  important  consideration:  Fick  has  demon- 
strated that  when  the  fibres  are  parallel  the  strength  of  two  muscles 
is  proportional  to  the  areas  of  their  cross-sections  (Hermann's  Hand- 
huch  der  Physiologie,  i.  p.  295).  The  average  ratio  of  the  diameter 
of  the  three  muscles  in  question  is  4  :  2  :  1,  respectively.  This  means 
that  with  the  same  leverage  the  biceps  would  lift  four  times  as  much 
as  the  brachialis  anticus  and  that  the  brachialis  anticus  would,  with 
the  same  leverage,  lift  four  times  as  much  as  the  supinator  longus. 

We  have  now  discussed  the  relation  of  these  three  factors  as  to 
leverage  and  as  to  relative  power  exerted. 

As  to  leverage  one  may  say:  The  power  of  the  three  muscles 
varies  in  proportion  to  biceps  leverage  (bl),  brachialis  anticus 
leverage  (al),  supinator  longus  leverage  (si),  respectively;  or,  mathe- 
matically expressed,  P  varies  as  bl :  al :  si  or  varies  as  16.6  :13.6:13.3. 
As  to  cross-section  one  may  say:  The  power  varies  in  proportion  to 
the  respective  cross-sections  (s),  or  P  varies  a.s  bs  :  as  :  ss=lQ  :  4  :  1. 
Now  when  any  function  varies  with  two  or  more  variable  factors, 
its  variation  when  influenced  by  the  action  of  all  of  these  factors  at 
once  would  be  represented  by  the  product  of  the  several  variables. 
Then  the  power  varies  as  the  leverage  times  the  cross-section  of  each 
of  the  muscles  when  all  act  together;  or,  expressed  mathematically, 
P  varies  as  b{lXs)  :  a{lXs)  :  s(lXs). 

6(ZX5)  =  16.6X16  =  265.6,  or  79.7  per  cent,  of  the  total  power  ex- 
erted; a(/X5)  =  13.6X4=54.4,  or  16.3  per  cent,  of  the  total  power 
exerted;  s(ZX5)  =  13. 3X  1  =  13.3,  or  4.0  per  cent,  of  the  total  power 
exerted;  total=  333.3,  or  100.0  per  cent. 

But  the  weight  supported  by  the  action  of  these  muscles  is  10  kilos. 
If  the  biceps  does  79.7  per  cent,  of  the  total  work,  it  would  support 
7.97  kilos.  What  would  be  tension  upon  the  tendon  of  the  biceps 
when  it  is  supporting  7.97  kilos  at  the  end  of  its  lever?  One  need 
only  to  use  the  16.6  per  cent,  leverage  (7.97 -=-16.6  per  cent.)  to  find 
that  the  tension  would  be  47.8  kilos.  A  similar  process  shows  that 
the  approximate  tension  upon  the  tendon  of  the  brachialis  anticus 
is  12  kilos,  and  upon  the  tendon  of  the  supinator  longus  3  kilos. 

b.  The  amount  of  contraction  of  a  muscle  bears  a  fairly  con- 
stant ratio  to  the  resting  length  of  the  muscle.  This  law  of  muscle 
physiology  was  discovered  and  demonstrated  by  Ed.  Fr.  Weber 
(Mechanik  der  menschlichen  Gehwerkzeuge,  1851)  and  was  cited 
by  Strasser  {Funktionellen  Anpassung  der  Quergestreiften  Muskeln, 
1883)  as  an  example  of  the  adaptation  of  muscle  tissue  to  the  mechan- 
ical requirements  of  the  body.     Weber  showed  that  the  maximum 


THE  PHYSIOLOGY  OF  THE  MUSCULAR  SYSTEM        225 

contraction  of  which  a  muscle  fibre  is  capable  is  approximately  47 
per  cent,  of  its  resting  length.  Both  Weber  and  Strasser  looked  upon 
this  as  the  factor  which  determines  the  length  of  the  muscles,  and  the 
location  of  their  points  of  origin  and  insertion.  In  all  of  the  skeletal 
muscles  the  tension  of  the  contracting  muscle  is  greater  than  the 
weight  lifted.  The  farther  the  insertion  of  a  muscle  from  a  joint 
(fulcrum),  the  less  the  tension  upon  the  muscle  and  the  greater  the 
amount  of  contraction  or  shortening  necessary;  but  the  inherent 
structure  of  striated  muscle  tissue  seems  to  set  47  per  cent,  as  the 
limit  of  the  extent  of  its  contraction.  The  fact  that  all  skeletal 
muscles  actually  do  contract  that  much  (varying,  however,  in  special 
instances  from  44  per  cent,  to  62  per  cent.)  indicates  that  the  position 
of  the  origin  and  insertion  or  the  length  of  muscle  tissue  (excluding 
tendon)  between  the  origin  and  insertion;  or,  more  likely,  that  both 
of  these  structural  features  have  been  determined  by  the  laws  of  selection 
and  now  represent  in  all  highly  organized  animals  the  most  perfect 
mechanical  a^justmejit  consistent  with  the  inherent  properties  of 
muscle^  tissue. 

(1)  Make  a  gastrocnemius  preparation;  measure  the  length  of  its 
contractile  tissue;  mount  it  in  the  myograph;  load  it  moderately; 
stimulate  it  with  optimum  strength  of  stimulus,  and  determine  from 
the  height  of  the  myogram  the  actual  shortening  of  the  muscle. 
What  relation  does  this  shortening  sustain  to  the  total  length  of  the 
contractile  tissue? 

(2j  Determine  approximately  the  ratio  of  shortening  to  length  of 
contractile  tissue  in  the  human  biceps. 

c.  Problems  in  Human  Locomotion.  (1)  The  Muscles  Used  in 
Locomotion.  Let  a  person  stand  erect  with  heels  together;  let  him 
take  several  steps  forward  and  stop  in  a  position  similar  to  the  one 
which  he  had  at  the  beginning.  What  is  the  mechanism  of  starting  f 
What  muscles  are  involved  in  starting?  What  is  the  mechanism  of 
locomotion?  What  muscles  are  involved  in  locomotion?  What  is 
the  mechanism  of  equilibration  while  walking?  What  muscles  are 
involved  in  maintaining  the  equilibrium  while  walking?  What  is 
the  mechanism  of  stopping f  What  muscles  are  involved  in  stopping? 
How  is  the  equilibrium  maintained  during  the  process  of  stopping? 
What  muscles  are  involved  in  the  maintenance  of  ecjuilibrium  while 
standing  ?  How  does  running  differ  from  walking  in  respect  to  the 
starting,  the  locomotion,  the  c(/uilihration,  and  the  stopping? 

(2)  The  Energy  Involved  in  Locomotion.  How  far  is  the  body  lifted 
at  each  ste[)  when  one  walks  over  a  level  surface?  When  one  walks 
up  an  incline  of  oO  degrees?  When  one  walks  down  an  incline  of 
•M)  degrees?  Does  one  do  work  while  walking  down  bill?  If  so, 
how  may  it  be  computed?  If  not,  why  does  one  become  fatigued  in 
descenriing  an  incline?  How  much  energy  will  a  70-kilo  man  expend 
in  walking  1  kilo  on  a  level  road?     (Suppose  the  man  to  be  172  cm. 

15 


226 


SPECIAL  PHYSIOLOGY 


in  height,  and  to  have  a  pubic  height  of  88  cm.)  A  part  of  the  energy 
will  be  expended:  (1)  in  hfting  the  body;  (2)  a  part  in  maintaining 
equilibrium;  (3)  a  part  in  overcoming  resistance.  Express  in  kilo- 
gram-metres the  amount  in  (1).    How  could  (2)  be  determined? 


II.  ERGOGRAPHY. 


The  term  ergography  applies  to  that  field  of  physiology  which 
deals  with  problems  of  work  done  by  individual  muscles  or  groups 


Fig.  85 


The  air-cushion  ergograph. 


of  muscles  in  the  human  subject.  The  instrument  used  is  the  ergo- 
graph.  This  instrument,  first  devised  by  INIosso,  has  undergone  many 
modifications  in  the  hands  of  Lombard,  Hough,  Bolton,  and  others. 


THE  PHYSIOLOGY  OF  THE  MUSCULAR  SYSTEM         227 

It  has  been  demonstrated  that  normally  the  muscle  works  under 
the  following  conditions:  (1)  contraction  with  load;  (2)  relaxation 
without  load  or  with  a  very  light  load;  (3)  rest  without  load.  This 
cycle  may  be  repeated  for  thousands  of  times  in  a  dav;  but  so  long 
as  these  conditions  are  filled  the  practised  muscle  can  work  for  three 
to  five  hours  without  fatigue,  unless  the  cycle  of  changes  is  too  rapidly 
repeated,  or  the  load  abnormally  heavy. 

These  are  some  of  the  problems  that  may  be  studied  in  the  field 
of  ergography. 

(1)  How  much  work  can  be  done  by  the  flexors  of  the  third  digit 
of  the  right  hand  before  fatigue  becomes  absolute — i.  e.,  before 
fatigue  makes  it  impossible  to  do  more  work  in  any  continuous  series 
of  contractions.    Conditions:  load,  5  kilo;  rate,  1  every  second. 

(2)  How  much  work  can  be  done  by  same  muscle  when  load  is 
3  kilos?     2  kilos? 

(3)  How  much  work  can  be  done  with  5  kilos  and  rate  1  every 
half-second  ? 

(4)  Determine  the  optimum  load  and  rate. 

1.  Appliances.  Ergograph  or  any  instrument  which  fulfils  the 
above  conditions  (Fig.  85  shows  such  an  instrument);  kymograph 
and  tracing  apparatus ;  metronome  to  mark  the  time. 

2.  Observation.  Adjust  the  splint  to  the  middle  finger  and  the 
arm  to  the  arm  rest.  Fasten  the  5-kilo  weight  to  the  splint;  adjust 
the  tracing  apparatus  and  kymograph  in  such  a  way  that  the  con- 
tractions every  two  seconds  will  result  in  a  tracing  with  a  straight 
abscissa,  with  lever  strokes  for  the  contractions  about  ^  mm.  apart. 
Set  the  metronome  to  beat  seconds. 

Let  the  subject  contract  once  per  second  to  a  moderate  extent,  and 
keep  it  up  regularly  until  fatigued. 

To  determine  the  work  done  proceed  as  shown  in  Lesson  XHL, 
p.  56. 

Use  similar  technique  for  various  problems,  varying  only  the 
details. 


APPENDIX. 


1.  NORMAL  SALINE  SOLUTION. 

This  solution  or,  as  it  is  also  called,  normal  salt  solution  or  physio- 
logical salt  solution,  is  so  much  used  in  the  physiological  laboratory 
that  it  should  be  made  in  considerable  quantity  and  always  easily 
accessible. 

Formula. 

Common  salt  (c.  p.) 30  grams. 

Distilled  water 5  litres. 

It  is  convenient  to  keep  the  solution  in  a  siphon  bottle.  It  is  thus 
protected  from  dust  and  evaporation,  and  is  always  easily  accessible. 


2.  FROG  BOARDS. 

There  is  probably  no  more  satisfactory  or  economical  frog  board 
than  a  piece  of  dressed  soft  pine  15  cm.  by  30  cm.,  and  1  or  2  cm. 
in  thickness.  Some  prefer  to  use  cork  board,  which  comes  in  pieces 
10  cm.  by  25  cm.  and  f  cm.  in  thickness.  In  the  case  of  either,  two 
or  three  coats  of  orange  shellac  should  be  given  to  the  boards  before 
they  are  put  into  use. 


3.  THE  PHYSIOLOGICAL  OPERATING  CASE. 

A  convenient  case,  and  one  which  will  be  sufficient  in  the  simple 
experiments  presented  in  this  book,  contains  the  following  instru- 
ments: one  medium  scalpel;  one  small  scalpel  with  narrow  blade; 
one  medium  scissors;  one  microscopic  scissors;  one  medium  dissecting 
forceps;  one  microscopic  forceps  with  curved,  serrated  jaws;  two 
serre-fine  forceps  with  stiff  springs  and  serrated  jaws;  one  grooved 
director  and  aneurysm  needle;  one  silver  probe;  one  blunt  needle 
for  pithing  frogs,  and  two  dissecting  needles. 

"^I'he  case  may  be  of  leather  or  leatherette.  Such  a  case  may  be 
used  nearly  as  much  in  the  histological  as  in  the  physiological  labor- 
atory. 


230  APPENDIX 

4.   GALVANIC  CELLS. 

For  general  use  in  the  physiological  laboratory  there  is  probably 
no  galvanic  element  superior  to  the  Daniell  cell  (named  after  Prof. 
J.  F.  Daniell,  of  King's  College,  London).  Much  the  most  con- 
venient and  economical  size  is  the  quart  or  litre  cell,  whose  porous 
cup  measures  5  to  6  cm.  in  diameter  and  10  to  12  cm.  in  height.  If 
more  current  is  needed  than  is  furnished  by  one  of  these  cells  it  is 
very  easy  to  join  two  or  more  of  them  into  a  battery. 

In  large  laboratories  it  will  be  found  expedient  to  devote  a  table 
to  the  galvanic  cells.  This  table  should  be  provided  with  a  supply 
of  copper  sulphate  and  of  10  per  cent,  sulphuric  acid  in  large  siphon 
bottles  similar  to  the  one  suggested  for  normal  salt  solution,  except 
that  instead  of  the  short  tube  for  equalizing  pressure  one  may  insert 
a  filter  through  which  at  the  end  of  the  laboratory  period  the  student 
may  return  the  liquids. 

The  accumulation  of  zinc  sulphate  in  the  acid  makes  the  renewal 
of  acid  necessary  from  time  to  time.  The  deposit  of  metallic  copper 
upon  the  copper  plate  reduces  the  copper  sulphate  solution  in  strength. 
It  may  be  kept  replenished  by  an  excess  of  crystals  of  that  salt  in 
the  large  supply  jar.  A  very  practical  method  of  amalgamating  the 
zinc  plates  is  to  have  a  jar  containing  10  per  cent,  sulphuric  acid 
with  mercury  in  the  bottom;  as  the  plate  is  immersed  the  acid  attacks 
it  and  cleans  it  so  that  the  mercury  readily  clings  to  it  and  may  be 
rubbed  over  the  surface  with  a  cloth.  Another  method  which  is 
preferred  by  some  is  as  follows: 

Dissolve  75  grm.  of  mercury  in  a  mixture  of  150  c.c.  strong 
nitric  acid  and  300  c.c.  strong  hydrochloric  acid.  Keep  this  amal- 
gamating solution  in  a  ground-glass-stoppered  jar.  To  amalgamate 
a  zinc  plate  one  needs  only  to  dip  it  for  a  few  moments  into  the 
solution,  remove  it,  rinse  under  the  spigot,  and  rub  with  a  cloth. 

At  the  end  of  each  laboratory  period  the  cells  should  be  emptied, 
the  zinc  plates  rinsed  and  drained,  and  the  porous  cups  left  in  a 
tray  of  running  water,  or  at  least  in  a  considerable  excess  of  water. 

5.  DRY  CELLS. 

For  a  part  of  the  work  in  electro-physiology,  particularly  electric 
stimulation  with  induction  shocks,  the  common  dry  cell  may  be  con- 
veniently used. 

The  dry  cell  becomes  rather  easily  'polarized  and  must,  therefore,  he 
used  on  an  open  circuit  only.  Used  in  this  way,  it  will  maintain 
its  strength  through  a  laboratory  period  and  will  recover  its 
original  condition  in  the  rest  which  intervenes  between  laboratory 
periods. 


A  FIXING  FLUID  FOR   CARBON  TRACINGS  231 

Most  dry  cells  consist  of  a  zinc  cup  or  can  enclosing  ammonium 
chloride  usually  mixed  with  plaster  of  Paris.  In  the  midst  of  the 
cell  is  a  carbon  plate  surrounded  by  manganic  dioxide. 

When  the  two  plates  (zinc  and  carbon)  are  joined  in  circuit  outside 
of  the  cell  the  XH^Cl  attacks  the  zinc,  forming  ZnCl,^  and  liberating 
NH4  and  H  at  the  carbon  plate.  This  tends  to  polarize  the  cell 
after  it  has  been  in  use;  but  during  the  rest  the  H  combines  with  O 
liberated  from  ]MnO,. 


G.  TO  CURARIZE  A  FROG. 

On  experiments  of  the  irritability  of  muscle  tissue  it  is  necessary 
to  in  some  way  suspend  the  activity  of  the  irritable  nerve  fibres 
which  are  supplied  to  every  muscle.  In  certain  other  experiments 
it  may  be  advisable  thus  to  remove  the  influence  of  the  nervous 
system.  Curara  (also  spelled  curare,  curari,  urari,  woorara,  woorari, 
wourali,  etc.),  an  arrow  poison  used  by  South  American  aborigines, 
is  the  means  usually  employed  to  accomplish  the  end  desired.  The 
way  in  which  the  curare  exerts  its  influence  is  made  the  suljject  of 
study  in  another  place.  Make  a  1  per  cent,  solution  by  pulverizing 
1  grm.  of  commercial  curare  and  dissolve  it  in  100  c.c.  of  distilled 
water.  It  need  not  be  filtered  unless  intended  for  use  with  a  hypo- 
dermic syringe.  If  kept  in  a  ground-glass-stoppered  bottle,  in  a 
cool  place,  it  will  retain  its  efficiency  for  months. 

The  most  convenient  method  of  curarizing  a  frog  is  to  inject  with 
a  narrow-pointed  pipette  1  to  3  drops  of  the  solution,  through  a 
minute,  ventral,  cutaneous  incision. 

The  drug  will  begin  to  take  effect  in  a  few  minutes.  The  maximum 
eft'ect  may  be  delayed  some  time. 


7.  TO  PREPARE  THE  KYMOGRAPH  FOR   WORK. 

Remove  the  cylinder,  stretch  a  sheet  of  the  prepared  glazed  paper 
tightly  upon  the  surface,  place  it  upon  such  a  stand  as  the  one  shown 
in  Fig.  33;  set  the  drum  to  rotating  and  bring  the  triple  gas  flame 
under  the  drum.  In  a  few  moments  it  will  be  evenly  covered  with 
a  film  of  carbon,  which  is  as  sensitive  to  touch  as  a  photographer's 
plate  is  to  light. 

8.  A  FIXING  FLUID   FOR  CARBON  TRACINGS. 

(;iiin  dariiar ICOK'hi. 

Benzole <l   »• '"'     aXM)  e.c. 

If  this  solution  be  ke[)t  in  a  large  inusciini  jar  in  tlic  laboratory, 
the  removed  sheet  bearing  the  tracings  may  be  dip|)i'(l  in  Mo  or  it  may 


232  APPExnix 

be  subdivided  and  dipped  in  sections.  Let  the  tracing  be  lowered 
quickly  into  the  solution  and  after  a  few  seconds  taken  out  and 
drained.  If  it  be  now  laid  upon  a  sheet  of  filter  paper  (or  a  news- 
paper) it  will  be  dry  in  a  few  minutes. 

9.  NON-POLARIZABLE  ELECTRODES. 

The  Du  Bois-Reymond  non-polarizable  (N.  P.)  electrode  is  made  as 
follows  (Fig,  86):  /,  glass  tube  of  about  4  mm.  lumen;  s,  zinc  rod 
^4th  binding  screw  (the  zinc  rod  must  be  amalgamated  before  use 
in  an  electrode) ;  r,  rubber  tube  clasping  both  glass  tube  and  zinc 
rod;  z$,  saturated  solution  of  sulphate  of  zinc,  introduced  with  a 
narrow-pointed  pipette;  K,  kaolin  plug,  made  by  working  China- 
clay  powder  into  a  stiff  paste  with  norm.al  salt  solution. 


Electrodes:  A,  kaolin  electrode  ;  z.  zinc  rod  ;  w,  saturated  solution  of  ZnSOi:  t,  glass  tube  ; 
r,  rubber  tube;  K,  plug  of  plastic  kaolin;  B,  v.  FleischVs  brush  electrode,  in  which  a  camel's- 
hair  brush  is  substituted  for  the  kaolin  plug;  C,  hand  electrodes,  made  by  pushing  the  com- 
mon battery  wires  through  rubber  tubing— for  insulation— and  binding  together  with  thread. 

The  electrodes  should  be  filled  at  each  time  of  using,  and  the 
parts  may  be  "assembled"  in  the  order  and  manner  enumerated 
in  the  description. 

The  Fleischl  brush  electrode  differs  from  the  foregoing  in  substi- 
tuting the  brush  of  a  camel's-hair  pencil  for  the  kaolin  plug.  This 
variation  of  the  non-polarizable  electrode  is  somewhat  more  difficult 
to  prepare,  but  is  more  convenient  for  certain  uses. 

Porter's  Non-polaxizable  Electrode.  This  electrode  is  boot-shaped 
and  is  the  most  convenient  form  for  general  laboratory  use.  The 
electrode  is  of  porcelain  with  glazed  leg  and  unglazed  foot. 

To  prepare  the  electrode  soak  it  in  normal  saline  solution  for  an 
hour  or  two  to  fill  the  pores  of  the  unglazed  portion  with  the  salt 
solution.  Fill  the  foot  of  the  boot  with  a  saturated  solution  of  zinc 
sulphate.  The  amalgamated  zinc  rods  may  be  dropped  into  the 
legs  of  the  boots  and  the  electrodes  are  ready  for  use. 

After  the  laboratory  period  pour  out  the  ZnSO^  and  put  the  boots 
in  running  water  or  in  a  considerable  excess  of  water  for  twelve  to 


THE  FROG-HEART  LEVER  233 

eighteen  hours  to  remove  any  ZnSO^  which  has  gained    access  to 
the  porous  portion  of  the  electrodes. 

If  one  has  not  the  zinc  rods  at  hand  he  may  readily  prepare 
an  efficient  non-polarizable  electrode  as  follows:  (1)  Take  5  cm. 
of  No.  16  copper  wire;  make  one  end  perfectly  clean  and  bright. 
(2)  Dip  the  bright  end  into  molten  chemically  pure  zinc.  The  zinc 
adheres  to  the  wire,  and  if  the  dipping  be  repeated  two  or  three  times 
the  lower  1  cm.  of  wire  will  have  a  thick  coating  of  zinc.  (3)  Take 
a  glass  tube  10  cm.  long  and  with  a  4  mm.  lumen;  draw  it  in  the 
middle  to  about  two-thirds  its  original  diameter;  cut  into  two. 
Before  assembling  the  parts,  that  part  of  the  copper  wire  not  covered 
by  zinc,  excepting  the  tip,  must  be  painted  with  Brunswick  black  or 
any  varnish,  and  the  zinc  must  be  amalgamated.  With  this  electrode, 
as  with  the  preceding,  zinc  sulphate,  kaolin,  and  0.6  per  cent.  NaCl 
are  used. 

10.  THE  FROG-HEART  LEVER. 

A  lever  for  recording  upon  the  kymograph  the  movements  of  a 
frog's  heart  may  be  constructed  very  simply  from  such  materials  as 
a  cork  2  cm.  in  diameter,  a  straw  30  cm.  long,  a  piece  of  parchment 
or  celluloid  for  a  tracing  point,  and  a  few  pins.  In  the  smaller  end 
of  the  cork  cut  a  groove  wide  enough  to  receive  the  straw  and  leave 
a  space  of  1  mm.  on  either  side.  The  groove  should  have  the  sides 
cut  perpendicular  to  the  end  of  the  cork  and  should  be  1  cm.  deep. 
Pass  a  pin  or  fine  needle  through  the  cork  in  such  a  way  as  to  cross 
the  groove  perpendicularly  and  about  2  or  3  mm.  away  from  the  end 
of  the  cork.  Partly  withdraw  the  pin  and  pass  it  through  the  straw 
or  lever,  ensuring  free  play  of  lever  in  the  groove  turning  on  the  pin 
as  a  fulcrum.  Let  6  cm.  of  the  straw  be  on  the  side  of  the  fulcrum 
and  24  cm.  on  the  other.  To  the  short  arm  a  counterpoise  may  be 
fastened,  and  to  the  long  arm  a  slender  cork  foot  may  be  fastened 
about  4  cm.  from  the  fulcrum  and  long  enough  to  reach  within 
1^  cm.  of  the  table  when  the  cork  fulcrum  stands  upon  the  table  and 
the  lever  is  horizontal.  To  the  distal  end  of  the  long  arm  fasten  a 
long,  slender  tracing  point  of  parchment  or  celluloid. 

To  adjust  such  an  apparatus  for  tracing  the  movements  of  the 
frog's  heart  one  has  only  to  place  the  cork  fulcrum  beside  a  frog 
prepared  as  described  on  page  75,  in  such  a  position  as  to  bring  the 
lower  end  of  the  cork  foot  into  the  required  position  upon  the  heart. 
When  adjusted  fix  in  position  by  passing  pins  through  the  edges  of 
the  cork  fulcrum  into  the  cork  plate  beneath. 

If  one  prefers  to  have  permanent  heart  levers  as  a  part  of  the 
laboratory  equipment  they  may  be  constructed  as  indicated  in 
Fig.  43.  ' 

Prof.  Porter,  of  Harvard,  has  devised  a  very  fine  heart  lever  which 
may  be  preferred  to  either  of  the  forms  descriU'd  above. 


234 


APPENDIX 


11.  THE  RESPIRATORY  CANNULA. 

In  experiments  involving  the  opening  of  the  thoracic  wall,  artificial 
respiration  must  be  maintained.  A  bellows  worked  by  hand  or  by 
machinery  will  be  required.  The  valves  of  the  bellows  open  inward 
only;  therefore,  some  vent  or  escape  must  be  furnished,  otherwise  the 
air  pressure  would  rise  too  high  within  the  lung  and  the  animal  would 
breathe  the  same  air  repeatedly. 

To  accomplish  the  desired  result  and  to  avoid  the  last-mentioned 
difficulties  Prof.  Ludwig  long  ago  devised  the  respiratory  cannula 
shown  in  Fig.  87,  A. 

Fig.  87 


Respiratory  cannulae:  A,  that  of  Ludwig,  metallic;  -B,  that  of  the  author,  of  glass. 

If  one  does  not  have  at  hand  a  Ludwig  respiratory  cannula  he  may 
quickly  and  easily  prepare  one  from  glass  that  will  answer  all  purposes. 
Several  of  these  of  different  sizes  should  be  prepared  so  that  when 
needed  one  may  select  a  size  best  fitted  to  the  animal  under  operation. 
Fig.  87,  B,  shows  the  construction  of  the  glass  respiratory  cannula. 


12.  TAMBOURS   (RECEIVING  AND  RECORDING). 

Next  to  the  kymograph  the  tambour  is  the  most  important  piece 
of  apparatus  in  the  physiological  laboratory.  They  are  used  almost 
daily  and  in  most  observations  of  changing  form  or  pressure.  Each 
completely  outfitted  table  should  have  the  recording  tambour  in  three 
sizes  and  receiving  tambours  of  various  shapes  and  construction. 

The  recording  tambour  must  vary  in  size  according  to  the  desired 
excursion  of  the  middle  of  the  membrane,  and  that,  in  turn,  will  vary 
with  the  amount  of  air  involved  in  the  to-and-fro  movement  in  the 
pressure  tube  and  tambours.  If  one  is  to  trace  the  movements  of 
the  human  thorax  in  respiration  he  will  want  a  capacious  receiving 
tambour  and  a  large  recording  tambour,  while  the  tracing  of  a 
sphygmogram  requires  a  very  small  recording  tambour. 

The  recording  tambour  consists  essentially  of  a  shallow  pan  1  to 
6  cm.  in  diameter,  from  which  a  tube  leads  to  the  pressure  tube 


TAMBOURS 


235 


connecting  the  receiving  tambour.  Across  the  pan  is  stretched,  not 
too  tightly,  a  sheet  of  very  Hght  dentist's  rubber-dam,  which  is  tied 
on  with  thread.  Upon  the  middle  of  the  tambour  membrane  there 
rests  the  foot  of  the  tracing  lever.  Through  this  foot  every  movement 
of  the  membrane  is  communicated  to  the  tracing  lever.    The  tracing 

Fig.  88 


Card. 


Sphyg. 


Pleth. 


¥ 


Steth.  Can. 

Receiving  tambours  for  various  purposes.  First  four  for  the  cardiograph,  sphygmograph ,  digital 
plethysmograph,  and  stethograph,  respectively.  The  last  one  (Can.)  is  a  thoracic  cannula  fnr 
use  in  determining  intrathoracic  pressure. 


lever  is  delicately  jjivoted  to  an  arm  which  extends  up  by  the  side 
of  the  pan  and  which  is  joined  to  the  tube  or  to  the  pan,  making  of 
the  tambour  and  lever,  with  its  supports,  one  apparatus.  Oidy  the 
lever  holder  should  be  metallie,  while  long,  light  straws  or  reeds  with 
tracing  points  of  parchment  or  celluloid   may  be  in.serted  into  the 


236  APPENDIX 

metallic  holder.  Each  tambour  should  have  a  set  of  levers  of  varying 
lengths — say,  10  cm.,  20  cm.,  and  30  cm.  Fig.  56,  page  106,  shows 
one  form  of  recording  tambour. 

The  receiving  tambours  must  be  constructed  with  a  view  to  their 
adaptation  to  each  particular  experiment.  The  receiving  tambour 
of  the  cardiograph  (Fig.  88,  Card.)  should  be  of  medium  size  and 
should  have  the  membrane  stretched  rather  tightly.  The  stetho- 
graphic  receiver  should  be  far  more  capacious,  having  perhaps  twice 
the  linear  dimensions  of  the  cardiographic  tambour,  and  the  mem- 
brane should  be  only  moderately  stretched.  The  recording  tambour 
should  be  of  the  largest  size  and  should  be  fitted  with  a  short  lever. 

The  sphygmographic  receiver  should  be  only  about  2  cm.  in 
diameter.  When  used  for  the  carotid  pulse  no  membrane  is  used. 
To  trace  the  radial  sphygmogram  a  membrane  with  a  button  is  used 
as  described  in  the  text. 

The  plethysmographic  receiver  is  used  to  determine  the  varying 
size  of  the  finger  incident  to  circulatory  changes.  The  finger  is 
inserted  through  the  rubber  collar.  The  record  is  made  by  the 
smallest  recording  tambour. 

The  cannular  receiver  is  used  for  taking  changes  in  intrathoracic 
and  intra-abdominal  pressure. 

13.  THE  MANOMETER  TAMBOUR. 

A  very  large  number  of  research  problems  require  the  recording 
blood  pressure  of  the  animal  (rabbit  or  dog)  under  observation.  In 
the  physiological  or  in  pharmacological  laboratories,  where  such  ob- 
servations are  in  progress  almost  daily,  it  is  not  difficult  to  get  satis- 
factory results  with  the  classical  apparatus,  which  consists  of  a  mercury 
manometer  whose  proximal  tube  (p)  is  joined  through  the  medium 
of  the  pressure  tubing  {Pt)  to  the  cannula  (C),  the  pressure  tubing 
being  interposed  at  (T)  by  a  T-tube,  one  limb  of  which  passes  to 
the  reservoir  containing  one-half  solution  of  MgSO^  or  some  other 
agent  for  retarding  coagulation.  Into  the  distal  limb  of  the  manom- 
eter {d)  there  is  fitted,  in  the  classical  apparatus,  a  float  which  rests 
on  the  mercury,  following  more  or  less  accurately  the  variations  in 
the  lever,  and  carrying  a  vertical  rod  which  slides  through  a  guide 
in  the  upper  end  of  the  distal  limb,  and  bears  at  its  upper  extremity 
a  horizontal  reed,  bearing  at  one  end  a  tracing  point. 

There  are  two  serious  difficulties  with  this  float.  First,  it  is  likely 
to  fail  to  work  properly  just  at  the  time  when  you  are  most  anxious 
that  there  should  be  no  interruption  in  your  observation,  though  if 
the  apparatus  is  in  almost  daily  use  this  difficulty  is  not  a  serious 
one.  The  serious  objection  against  the  float  is  that  it  does  not  follow 
accurately  the  movement  of  the  mercury.  The  mercury  starts  up 
a  little  before  the  float  does,  and  the  float  itself  has  so  much  inertia 


THE  STETHOGRAPH  237 

that  the  actual  movements  of  the  mercury  are  not  shown  at  all  by 
it.  In  order  to  overcome  this  difficulty,  and  to  be  able  to  record 
accurately  the  movements  of  the  mercury  meniscus,  the  following 
variation  of  the  classical  apparatus  was  contrived: 

A  small  tambour  was  joined  to  the  distal  end  of  the  manometer 
by  a  piece  of  pressure  tubing  and  supplied  with  a  very  delicate 
tracing  lever  which  magnifies  the  movements  of  the  membrane  ten 
to  twenty  times,  as  desired,  the  levers  being  variable  in  the  con- 
struction of  the  instrument.  The  surface  of  the  tambour  should  not 
be  larger  than  15  mm.  in  diameter.  With  this  ratio  between  the  two 
surfaces  and  the  levers  multiplying  ten  to  twenty  times,  the  most 
beautiful  arterial  tracing  can  be  obtained,  showing  not  only  the 
respiratory  and  percussion  waves,  but  also  the  dicrotic  wave  clearly 
superimposed  on  each  cardiac  wave.     (See  Fig.  52,  page  92.) 

This  apparatus  as  above  described  has  one  limitation,  which  may, 
for  certain  kinds  of  work,  seem  to  be  a  disadvantage.  The  pressure 
tubing  leading  from  the  distal  end  of  the  manometer  to  the  tambour 
{Th)  is  not  attached  to  the  manometer  until  after  the  rise  of  the 
mercury  in  the  distal  tube  following  the  removal  of  the  clamp  {CI). 
After  the  tambour  is  attached  to  the  manometer  every  movement  of 
the  mercury  is  shown  by  corresponding  movements  of  the  tracing 
point  {t).  Should  there  be  a  sudden  rise  or  sudden  fall  of  pressure, 
it  will  be  instantly  and  clearly  shown  by  corresponding  rise  and  fall 
of  the  tracing.  Should  there  be,  however,  a  very  gradual  rise  or  a  very 
gradual  fall,  owing  to  physiological  changes  in  tonus  of  the  blood- 
vessels, for  example,  or,  perhaps,  by  the  gradual  action  of  some  drug 
on  the  animal  under  observation,  this  will  not  be  shown  by  corre- 
sponding rise  and  fall  of  the  tracing.  It  will,  however,  be  shown  by 
the  stand  of  mercury  in  the  distal  limb  of  the  manometer,  and  this 
may  be  easily  read  off  or  noted  from  time  to  time. 

To  offset  this  slight  disadvantage  one  has  the  two  advantages 
above  mentioned,  namely,  accuracy  of  the  tracing  of  all  the  quicker 
movements  of  the  mercury  and  the  assurance  that  one's  apparatus 
will  always  work. 

14.  THORACIC  CANNUL.ffi. 

A  cannula  for  transmitting  the  air  pressure  from  the  pleural  or 
mediastinal  or  abdominal  cavity  may  be  easily  constructed  as  follows: 
Take  a  piece  of  ordinary  soft  and  thin-walled  glass  tubing  about 
10  cm.  in  length  and  3  cm.  himcii.  Griiifl  one  end  diagonally  sharp 
as  shown  in   Fig.  8S,  Can. 

1,',.  THE  STETHOGRAPH. 

In  order  to  record  gra})lii(ally  the  movements  of  the  chest  one  may 
use  various  mechanical  devices.    The  most  simple  device,  and  a  most 


238  APPENDIX 

effective  apparatus,  when  only  the  time  relations  and  the  character 
of  movements  are  matters  of  concern,  is  the  instrument  which  involves 
the  use  of  two  tambours,  a  receiving  and  recording  tambour.  The 
latter  one  is  described  above  (12). 

A  receiving  tambour  may  be  constructed  especially  for  this  purpose 
as  follows:  Take  a  large  thistle  tube,  cut  off  its  funnel  with  8  or 
10  cm.  of  the  tube,  stretch  across  it  loosely  a  piece  of  thin  sheet 
rubber  and  fasten  this  tightly  as  shown  in  Fig.  88,  Steth.  To  the 
middle  of  the  rubber  diaphragm  fasten  a  long  cork,  using  glue  or 
sealing-wax. 

The  stethograph  complete  consists  of  a  thoracic  frame,  as  shown 
in  Fig.  58,  and  of  the  tambours,  the  recording  tambour  being  held 
by  an  extra  support  as  usual. 

The  thoracic  frame  is  very  simply  constructed  of  pieces  of  half- 
inch  glass-pipe  supported  by  a  heavy  stand  and  clamps  as  shown  in 
the  figure. 

The  receiving  tambour  is  held  in  a  clamp,  its  location  upon  the 
bar  being  readily  adjusted.  The  width  of  the  frame  and  its  height 
are  both  easily  adjustable. 


16.  THE  CHEST  PANTAGRAPH. 

Fig.  59  shows  the  instrument,  which  is  constructed  of  brass  or  wood 
with  brass  or  steel  semicircle.  The  joints  a,  b,  x,  and  y  move  easily 
in  the  plane  of  the  instrument.  The  semicircle,  40  inches  in  diam- 
eter, rotates  at  x  around  the  diameter  t  x.  The  point  /  is  fixed  to 
a  table.  With  /  a  fixed  point  all  movements  of  t,  the  tracing  point, 
are  accompanied  by  corresponding  movements  of  r,  the  recording 
point.  The  triangles  /,  r,  b  and  /,  t,  a  are  similar  triangles  in  all 
positions  of  the  instrument  fb  :  fa  :  :  fr  :  ft ;  but  fb :  fa: :  1:5;  there- 
fore, the  distance  fr  is  always  one-fifth  the  distance  ft. 

The  object  of  the  semicircular  arm  is,  of  course,  to  permit  the 
tracing  point  t  to  be  carried  around  the  thorax.  The  seat  upon 
which  the  subject  sits  is  adjustable  in  height  and  back  and  side 
supports  for  the  waist,  so  that  the  upper  part  of  the  body  is  not 
allowed  to  waver  from  side  to  side,  distorting  the  contour.  If  the 
subject  to  be  examined  sit  beside  the  table  on  which  the  instrument 
is  fixed;  if  the  seat  be  adjusted  in  height  to  bring  the  plane  of  the 
thorax  to  be  examined  into  the  plane  of  the  instrument — i.  e.,  on  a 
level  with  the  top  of  the  table;  if  a  sheet  of  millimetre  paper  be  fixed 
to  the  table  under  the  recording  pencil  r;  and  if  the  tracing  point  t  be 
swept  around  the  thoracic  wall,  a  record  of  the  chest  contour  will 
be  traced  upon  the  paper. 

The  accompanying  Fig.  89  shows  two  such  contours  from  healthy, 
well-developed  young  men.    Two  millimetres  in  the  figure  equal  one 


THE  CHEST  PANT  A  GRAPH 


239 


centimetre  of  actual  measurement.     The  inner  contour  is  that  of 
forced  expiration,  while  the  outer  one  is  that  of  forced  inspiration. 


Contours  of  cheats,  taken  with  cliest  i)aiitiiKiiii)h 


In  contour  A  the  infrease  of  lateral  diameter  by  forced  inspiration 
i.s  2  cm.,  while  the  increase  of  dorsoventral  is  -i  cm.     In  the  same 


240  APPENDIX 

contour  the  cross-sectional  area  of  the  thorax  in  the  plane  of  the 
ninth  rib  is  represented  by  25.52  of  the  larger  squares  containing 
25  square  cm.;  total  area  equals  637.5  square  cm.,  while  the  cross- 
sectional  area  of  the  chest  in  forced  expiration  is  517.5  square  cm. 
Forced  inspiration  shows  an  increase  of  120  square  cm.,  or  about 
23  per  cent.,  over  cross-sectional  area  of  forced  expiration.  Further- 
more, both  contours  show  a  prominence  in  the  right  side  (left  of  the 
figure),  possibly  due  to  stronger  musculature  on  that  side. 


17.  THE  PNEOMANOMETER. 

This  instrument  may  be  easily  constructed  in  the  laboratory. 
Take  a  piece  of  heavy  glass  tubing  7  to  9  mm.  lumen  and  at  least 
160  cm.  in  length.  Bend  it  as  shown  in  Fig.  61.  A  covered  filter 
may  be  attached  as  shown  in  the  figure  if  there  is  any  tendency  for 
the  mercury  to  be  thrown  out. 


i:n^de 


A 


Absorption,  176 
Accommodation,   188 

range  of,  200 
Acid,  hydrochloric,  168 
Aconite,  action  of,  104 
Action  of  curare,  212 

of  strychnine,  210 

of  veratrin,  214 

reflex,  206 
Adrenalin,  action  of,  104 
Albumin,  acid,   162 

egs,   162 
Alcohof,  27 

influence  on   ciliary  motion,   35 
Alga?,  21 

motile,  23 

non-motile,  21 
Amalgamation  of  zinc,  37 
AmoeBa,  25-28 

reproduction  of,  28 
Ampere,  40 

Ana-sthesia,  study  of,  97 
Anatomy,  frog's  thigh  and  leg,  47 
Anelectrotonus,  62,  63 
Angle,  visual,  197 
Animal  mechanics,  222 
Anode,  influence  of,  58-60 
Anthropometric  data,  113 
Apex  beat  of  heart,  79 
Aquaria  for  alga-,  25 
Artery,  radial,  location  of,  89 
Atropine,  action  of,  on  heart,  101 


B 


Batteries,  41 

Battery,  in  multiple  arc,  42 
in  series,  43 

Bile,  174 

action  on  foods,  175 

Biuret  test,  163 

Blind  spot,  192 

Blood,  centrifugalization  of,  137 
circulation  of,  73 
classification  of  leukocytes,  154 
coloring  matter  to  estimate,  138 
corpuscles,  counting,   130 
counter,    'I'lioma-Zeiss,    130 


Blood,  examination  of  fresh,  148 
films,  fixing  of,  151 

staining  of,   153 
microscopic  examination  of,  148 
pressure  apparatus,  92 

in  tissues,  99 

laws  of,  86 

to  determine,  91 
spreading  of  films,  150 
Bone-marrow,  staining,  155 


Cannula,  respiratory,  234 
Cannulse,  thoracic,  237 

tracheal,  109 
Capacity  of  lungs,  113 
Capillary   circulation,   73 

electrometer,  66,  67  ^ 

pressure,  99 
Carbohydrates,  157 

classification,    159 
Carbon  dioxide,  determination  of,  117 
excretion  of  yeast,  27 
influence  on  cells,  29 

on  ciliary  motion,  33 
plant  food,  25 

monoxide,  effect,   125 
Cardiogram,  79,  80 
Cardiograph,   79 
Cardiopneumatogram,  108 
Catelectrotonus,  62,  63 
Cathode,  influence  of,  58-60 
Cell,  Daniell,  37 

electric,  work  done  by,  40 
Cells,  dry,  230 

galvanic,  230 
Centrifugalization  of  blood,   137 
Chest  measurement,  113 

pantagraph.  111,  238 
Chloroform,  influence  on  ciliarv  motion, 

34 
Chlorophyll  in  alga?,  22 
Cilia,  work  done  by,  35 
Ciliarj'  motion,  31 

influenced  by  COj,  33 
Circuit,  primary,  51 

secondary,  51 
[  Circulation,  73 
'  capillary,  73 

16 


242 


INDEX 


Classification  of  leukocytes,  154 
Coagulation  of  normal  blood,  148 
Color  sense,  test  of,  199 
Commutator,  39 

Pohl's,  38,  39 
Conductivity,  63 
Conjugation,  23 
Contours  of  chest,  239 
Contraction,  law  of,  64 
Contractions,  stair-case,  55 
Convergence,  188,  190,  191 
Corpuscles,  white,  to  count,  135 
Counting  blood  corpuscles,  130 

differential,  153 
Curare,  action  of,  212 
Curarization  of  frog,  231 
Current,  polarizing,  62,  63 

strength  of,  varied,  43 
Cytology,  21 


D 


Daniell  cell,  37 

Dare's  hEemoglobinometer,    144 

Data,  anthropometric,  113 

evaluation  of,  115 
Desmids,  21 

Diaphragm,  observation  of,  127 
Diatoms,  23 

Diffusibility  of  proteids,  164 
Digestion,  156 

gastric,  167 

steps  of,  171 

intestinal,  174 

salivary,  159 

steps  of,  161 
Digitalis,  action  of,  on  heart,  103 
Dileptus,  25 
Dioptric  system,  185 
Dissection  of  eye,  178 
Du  Bois-Reymond  key,  38 


E 


T]gg  albumin,  162 
Elasticity  of  lungs,  108 
Electric  cell,  work  done  by,  40 

units,  40 
Electricity,  37 

influence  on  irritability,  61 
Electrode,  negative,  38 
Electrodes,  non-polarizable,  58,  232 

positive,  38 

shielded,  95 
Electrometer,  66,  67 

capillary,  68 
Electromotive  force,  41 
Electrotonus,  61 

laws  of,  64 
Element,  Daniell,  37 
Emulsification  of  fats,  173 
Eosinophile,  154,  155 


Ergograph,  226  'i 

Ergography,  226 
Euglena,  28,  29 
Evaluation  of  data,  115 
Examination  of  fresh  blood,  148 

post-mortem,  124 
Eye  dissection,   178 

emmetropic,  198, 200,  202,  203, 204 
J 


Falling  bodies,  laws  of,  82 
Far-sightedness,  199 
Fatigue,  56 
Fats,  172 

emulsification,  173 

saponification,  173 

solubility,  172 
Fehling's  solution,  157 

test,  158 
Films,  fixing  of  blood,  151 

staining  of  blood,  153 
Fixation,  monocular,  191 
Fixing  of  blood  films,  151 
Fleischl's  hsemometer,  139,  140 

rheonome,  56,  57 
Fluid,  Pasteur's,  26 
Focal  distance  of  lenses,  183 
Force,  electromotive,  of  muscles,  69 

intermittent  and  inelastic  tubes,  84 
Frog  boards,  229 

myograph,  50,  51 

to  curarize,  231 

pithing,  31 

rheoscopic,  69,  70 
Frog's  heart  action,  74 

beat,  graphic  record,  75 
lever,  237 

leg,  anatomy  of,  47 
Function  of  spinal  nerves,  220 
Fungi,  26 

'G 

Galvanisms,  61 
Galvanometer,  Wiedemann,  66 
Galvanoscope,  44 
Gastric  digestion,  factors  of,  168 

steps  of,  171 
juice,  artificial,  167 

standard,  169 
Gastrocnemius,  stimulation  of,  49 
Gemmation,  26,  27 
Glass  nerve  hook,  48 
Gmelin's  test  for  bile,  175 
Gowers'  hsemoglobinometer,  142,  143 


H 

HtEmacytometer,  Oliver,  132 
Hematocrit,  131,  137 
Hsematology,  normal,  128 


INDEX 


243 


Haemoglobin,  to  estimate,  138 

and  specific  gravity,  146 
Hsemoglobinometer,   142,   143 

Dare's,  144 

TaUquist's,  145 
Hsemometer,  Fleischl's,  139,  140 
Hammerschlag's  table,  147 
Heart,  apex  beat,  79 

as  influenced  by  atropine,  101 
by  digitalis,  103 
bj'  pilocarpine,  102 

of  frog  in  action,  74 

movements  of  mammalian,  76 

to  expose  mammalian,  77 
Hyperopia,  199,  200,  202,  203,  205 


Index  of  refraction,  182 
Induction  shocks,  54 
Inductorium,  50,  51 
Infusoria,  28 
Intestinal  digestion,  174 
Irritability,  63 

influenced  by  electricity,  61 


K 

Key,  contact,  38 

Du  Bois-Reymond,  38 

short-circuiting,  38 
Keys,  38 
Kymograph,  52 

support,  52 

to  prepare,  231 


Latent  period,  55 
Law  of  contraction,  64 

of  Torricelli,  81 

Ohm's,  40 
Laws  of  blood  pressure,  86 

of  electrotonus,  64 
Lens,  focal  distance  of,  183 
Lenses,  numeration  of,  196 
Leukocytes,  classification  of,  154 
Liminal  intensity  of  stimulus,  53 
Liquids,  flow  of,  through  tubes,  81,  84 
Locomotion,  human,  225 
Lung  capacity,  113 
Lungs,  elasticity  of,  108 


M 

Manometer,  87 

tambour,  92,  236 
Marriotte's  expf;rimcnt,  192 


Measurements  of  chest,  113 
Mechanics,  animal,  222 
Megaloblast,  155 
Megalocyte,  155 
Mercury,  37 

manometer,  87 
Microblast,  155 
Microcyte,  155 
Milk,  165 

digestion  of,  172 
Millon's  reagent,  162 

test,  163 
Motion,  ciliary,  31 
Movements,  thoracic,  106 
Multiple  arc  batter}',  42 
Muscle,  electromotive  phenomena  of,  69 

nerve  preparation,  46,  48 

signal,  61 

tissue,  general  physiology  of,  37 

work  done  by,  55 
Muscular  system,  222 
Myelocytes,  155 
Myogram,  54 
Myograph  as  pulse  writer,  85 

double,  58,  59 

frog  board,  50 

simple,  47 
Myopia,  199,  200,  203,  204 
Myosin,  162 


N 


Near-sightedness,  199 

Neef  Hammer,  51 

Nerve  hook,  48 
phrenic,  125 
vagus,  action  of,  95 

Nerves,  function  of  spinal,  220 

Nervous  system,  206 

Neutrophile,  154,  155 

Nitric  acid  test,  163 

Non-polarizable  electrodes,  58 

Normoblast,  155 

Normocyte,  155 


O 


CEsoPHAGUS,  removal,  31 

Ohm's  law,  40 

Operating  case,  229 

Ophthalmoscopy,  201 

Optics,  physiological,  181 

Optimum  intensity  of  stimulus,  53 

Oscillaria,  24,  25 

Osmic  acid  test,  1 72 

Oxygen,  determination  of,  119,  120 


Pancreatic  extract,  174 

juice,  action,   175 
Pantagraph,  HI,  238 


244 


INDEX 


Paramcecium,  28,  30 

Pasteur's  fluid,  26 

Pepsin,  glycerin  extract  of,  167 

Perimeter,  194 

Perimetry,  193 

Period,  latent,  55 

Pfiiiger's  law  of  contraction,  65 

Phrenicus,  nervxis,  125 

Phrenogram,  125 

Phrenograph,  126 

Physiological  optics,  181 

Physiology,  general,  21 

special,  73 
Piezometers,  83 

Pilocarpine,  action  on  heart,  102 
Pithing  frogs,  31 

influence  of,  on  nervous  system,  206 
Plasma,  determination  of,  137 
Plate  negative,  38 

positive,  38 
Plethysmograph,  100 
Pneomanometer,  112,  240 
Pneumdtogram,  108 
Pohl's  commutator,  38,  39 
Poikilocyte,  155 
Pole  changer,  38 

negative,  38 

positive,  38 
Post-mortem  examination,  124 
Pressure  of  blood  in  tissue,  99 

capillary,  99 

intermittent,  influence  of,  89 

intrathoracic,  106,  107 

laws  of  blood,  86 

of  pulse,  93 

respiratory,  108,  113 
Proteids,  161 

diffusibility  of,  164 
Protococcus,  21 
Protozoa,  28 
Pseudopodia,  28 
Pulse,  84 

carotid,  90 

pressure,  93 

radial,  88 
Punctum,  proximum,  189 

remotum,  189 
Putrefaction  in  stomach,  170 

Q 

Quotient,  respiratory,  120,  121 

R 

Reaction  changes  in  fatigue,  56 
Reflex  action,  206 
Reflexes,  208 

circulatory,  209 

cutaneous,  210 

of  deglutition,  209 

respiratory,  209 


Reflexes,  secretorj^,  209 

"tendon,"  210 

\dsual,  209 
Refraction,  index  of,  182 
Region,  extrapolar,  64 

intrapolar,  64 
Reproduction  in  amoeba,  28 

in  protococcus,  22 

in  yeast,  27 

spirogyra,  23 
Reservoir  for  h3'draulics,  81 

with  piezometers,  83 
Resistance,  electric,  41 

peripheral,  86 
Respiration,  106 

closed  space,  124 

in  COo,  124 

in  illuminating  gas,  125 

to  induce  artificial,  77 

under  abnormal  conditions,  123 
Respiratory  pressure,  108,  113 

quotient,  120 
Rheocord,  simple,  45 
Rheonome,  Fleischl's,  56,  57 
Rheoscope,  physiological,  69,  70 
Rheostat,  42,  43 
Rhizopoda,  28 


S 


Saccharomyces,  26 

Salivary  digestion,  steps  of,  161 

extract,  159 

secretion,  159 
Saponification  of  fats,  173 
Scheiner's  experiment,  192 
Sensation,  215 

auditory,  220 

gustatory,  219 

muscular,  219 

of  equilibrium,  218 

tactile,  216 

temperature,  217 
Shocks,  induction,  54 
Skiascopy,  204 
Solution,  normal  saline,  229 
Specific  gravity  and  haemoglobin,  146 
Sphygmogram,  88,  89 
Sphygmograph,  88,  89 

Porter's,  90 
Sphygmomanometer,  93,  94 
Spinal  nerves,  function  of,  220 
Spirogyra,  22 
Spirometer,  112 
Spores,  swarm,  24 
Spreading  blood  films,  150 
Staining  blood  films,  153 

bone-marrow,  155 
Stair-case  contractions,  55 
Starch  in  spyrogyra,  22 
Steps  of  gastric  digestion,  171 

of  salivary  digestion,  161 


INDEX 


245 


Stethogram,  110 
Stethograph,  110,  237 
Stethoscope,  80 
Stimulation,  chemical,  49 

electric,  49,  50 

indirect,  49 

mechanical,  49 

thermal,  49 
Stimulus,  liminal  intensity,  53 

optimum  intensity,  53 
Strj-chnine,  action  of,  210 
Surface  tension,  67 
Sjinpathetic,  action  of,  98 

cardiac,  action  of,  97 
S5Titonin,  162 
System,  artificial  circulatory,  86,  87 


Tallquist's  ha^moglobinometer,   145 
Tambour,  manometer,  92,  236 

recording,  106 
Tambours,  234 
Temperature,  optimiun,   for  digestion, 

171 
Tension,  surface,  67 
Test,  biuret,  163 

cold  nitric  acid,  163 

Gmelin's,  175 

Fehling's,  158 

heat,  162 

Millon's,  163 

of  color  sense,  199 

osmic  acid,  172 

Trommer's,  158 

xanthoproteic,  163 
Tetanus,  54 
Thallophytes,  26 
Thoma-Zeiss  counter,  130 
Thorax,  human,  110 

movements  of,  106,  110 
Torricelli,  law  of,  81 
Tracings,  to  fix,  231 


Trommer's  test,  158 

Tubes,  elastic,  influence  of,  84 


U 


Units,  electric,  40 


Vagus  nerve,  action  of,  95,  98 

dissection  of,  96 
Value,  median,  115 
Veratrin,  action  of,  214 
Vision,  178 

acuteness  of,  196 
Volts,  41 

Volume  of  red  blood  corpuscles,  137 
Vorticella,  28,  31 


W 

Water,  determination  of,  117 
Wave,  impulse,  84 
Work,  56 

amoimt  done  by  cilia,  35,  36 
by  muscle,  55 

reaction  changes,  56 


X 

Xanthoproteic  test,  163 

Y 

Yeast  plant,  26 

Z 

Zinc,  amalgamation  of,  37 


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CORNIL   (V.).     SYPHILIS:   ITS  MORBID   ANATOMY,  DIAGNOSIS  AND 
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DRUITT  (ROBERT).     THE  PRINCIPLES  AND  PRACTICE  OF  MODERN 

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DUANE  (ALEXANDER).  A  DICTIONARY  OF  MEDICINE  AND  THE 
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and  revised.     8vo.  of  880  pages,  with  150  original  engravings.     Cloth,  $5 ;  leather,  $6. 

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2316  pages,  with  984  engravings.     Cloth,  |9;  leather,  $11. 

ESSIG   (CHARLES   J.).      PROSTHETIC    DENTISTRY.    Second   editicn.      See 

American  Text-books  of  Dentistry,  page  2. 

ESSIG(C.  J.)  AND  KOENIG  (AUGUSTUS).  DENTAL  METALLURGY.  New 
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EVANS  (DAVID  J.).     A  POCKET  TEXT-BOOK  OF  OBSTETRICS.     12mo. 

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FERGUSON'S  EPITOME  OF  THE  NOSE  AND  THROAT.  Lea's  Series  of  Med- 
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FIELD  (GEORGE  P.).  A  MANUAL  OF  DISEASES  OF  THE  EAR.  Fourth 
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FINDLEY  (PALMER  D.).  A  TREATISE  ON  GYNECOLOGICAL  DIAG- 
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FLINT  (AUSTIN).  A  TREATISE  ON  THE  PRINCIPLES  AND  PRACTICE 
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In  one  large  8vo.  volume  of  1143  pages,  with  engravings.     Cloth,  $5 ;  leather,  $6. 


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FOTHERGILL  (J.  MILNER).  HAND-BOOK  OF  TREATMENT.  Third  edition. 
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FOWNES  (GEORGE).  A  MANUAL  OF  ELEMENTARY  CHEMISTRY. 
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FULLER  (EUGENE).  DISORDERS  OF  THE  SEXUAL  ORGANS  IN  THE 
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OALLAUDET  (BERN  B.).  A  POCKET  TEXT-BOOK  OF  SURGERY. 
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Text-Booh.     Page  12. 

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GAYLORD  (HARVEY  R.)   AND  ASCHOFF   (LUDWIG).    PATHOLOGICAL 

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pages,  with  81  engravings  and  40  full-page  j)lates.     Cloth,  $7.50,  net. 

OERRISH  (FREDERIC  H.).  A  TEXT-BOOK  OF  ANATOMY.  By  American 
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GRAY  (HENRY).  ANATOMY,  DESCRIPTIVE  AND  SURGICAL.  Fifteenth 
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GREENE  (WILLIAM  H.).  MEDICAL  CHEMISTRY.  12mo.,  310  pages,  with 
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GRINDON  (JOSEPH).     A    POCKET   TEXT-BOOK   OF  SKIN  DISEASES. 

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HALE  (HENRY  E.).  AN  EPITOME  OF  ANATOMY.  12mo.,  389  pages,  71 
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HAMILTON  ( ALLAN  McLANE).  NERVOUS  DISEASES.  Second  and  revised 
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HAMILTON    (MILDRED    M.).     A   POCKET  TEXT-BOOK   OF  MASSAGE. 

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Editor.     A  SYSTEM  OF  PRACTICAL  THERAPEUTICS.     By  American 


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HARRINGTON  (CHARLES).  A  TREATISE  ON  PRACTICAL  HYGIENE. 
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HARTSHORNE  (HENRY).  A  CONSPECTUS  OF  THE  MEDICAL  SCIENCES. 
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Medicine,  Surgery  and  Obstetrics.  Second  edition.  12mo.,  1028  pages,  with  477  illustra- 
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HAYDEN  (JAMES  R.).  A  POCKET  TEXT-BOOK  OF  VENEREAL  DIS- 
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HOLLIS"  EPITOME  OF  MEDICAL  DIA  GNOSIS.  Lea's  Series  of  Medical  Epitomes. 
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A  SYSTE3I  OF  SURGERY.     Edited  by  John  H.  Packard,  M.D.      In  three 


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HUNTINGTON  (GEORGE  S.).  ABDOMINAL  ANATOMY.  Imperial  quarto, 
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HYDE  (JAMES  NEVINS)  AND  MONTGOMERY  (FRANK  H.).  A  PRAC- 
TICAL TREATISE  ON  DISEASES  OF  THE  SKIN.  Sixth  edition,  thoroughly 
revised.  Octavo,  832  pages,  with  107  engravings  and  27  full-page  plates,  9  of  which 
are  colored.     Cloth,  $4.50,  net;  leather,  $5.50,  net;  half  morocco,  $6.00,  net. 

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JAMIESON  (W.  ALLAN).  DISEASES  OF  THE  SKIN.  Third  edition.  Octavo, 
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JEWETT  (CHARLES).  ESSENTIALS  OF  OBSTETRICS.  Second  edition. 
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THE  PRACTICE  OF  OBSIETRICS.     By  American  Authors.    Second  edition. 

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JULER  (HENRY).  A  HANDBOOK  OF  OPHTHALMIC  SCIENCE  AND 
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KELLY  (A.O.J.)  A  3IANUAL  OF  THE  PRACTICE  OF  MEDICINE. 
Octavo,  about  COO  pages,  illustiated.     Preparing. 

KIEPE  'EDWARD  J.).  EPITOME  OF  MATERIA  MEDICA  AND  THERA- 
PEUTICS.    Leu' s  Series  of  Medical,  Epitomes.     See  page  10. 

KING  (A.  F.  A.).  A  MANUAL  OF  OBSTETRICS.  Ninth  edition.  In  one 
12mo.  volume  of  629  pages,  with  275  illustrations.     Cloth,  $2.50,  net. 

KIRK  (EDWARD  C).  OPERATIVE  DENTISTRY.  Second  edition.  See 
American  Texl-bookn  of  Dentistry,  page  2, 

KLEIN  (E.I.  ELEMENTS  OF  HISTOLOGY.  Fifth  edition.  In  one  pocket-size 
12mo.  volume  of  506  pages,  with  296  engravings.  Cloth,  $2.00,  net.  Students'  Series  of 
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KOPLIK  ( HENRY ) .  DISEA  SES  OF  INF  A  NC  Y  AND  CHIL  DIIOOD.  Octavo, 
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MANTON  (W.  P.).  AN  EPITOME  OF  OBSTETRICS.  12ino.,  265  pages,  82 
illustrations.     Cloth,  $1.00,  ?ie<.     Lea's  Series  of  Medical  Epilomes.     See  page  10. 

MANUALS.     See  Medical  Epitomes,  page  10  ;  Pocket  Texl-Books,  page  12. 

MARSH  (HOWARD).  DISEASES  OF  THE  JOINTS.  In  one  12mo.  volume  of 
468  pages,  with  64  engravings  and  a  colored  plate.  Cloth,  $2.  See  Series  of  Clinicai 
Manuals,  page  13. 

MARTIN  (EDWARD.)  SURGICAL  DIAGNOSIS.  One  12mo.  volume  of  400 
pages,  richly  illustrated.     Preparing. 

MARTIN  (WALTON)  AND  ROCKWELL  (W.  H.,  JR.).  A  POCKET  TEXT- 
BOOK OF  CHEMISTRY  AND  PHYSICS.  12mo.  366  pages,  with  137  illus- 
trations. Cloth,  $1.50,  net;  flexible  leather,  $2.00,  net.  Lea's  Series  of  Pocket  Text- 
Books.     Page  12. 

McGLANNAN  (A.).  AN  EPITOME  OF  INORGANIC  CHEMISTRY  AND 
PHYSICS.  12mo,  216  pages,  with  20  engravings.  Cloth,  $1.00,  net.  Lea's  Series  of 
Medical  Epitomes.     See  page  10. 

AN  EPITOME  OF  ORGANIC  AND  PHYSIOLOGICAL  CHEMISTRY. 


12mo.,  246  pages,  with  9  engravings.    Cloth,  $1.00,  net.    Lea's  Series  of  Medical  Epitomes. 
See  page  10. 

MEDICAL  EPITOME  SERIES.     See  Lea's  Series  of  Medical  Epitomes,  page  10. 

MEDICAL  NEWS  POCKET  FORMULARY.    See  page  1.    $1.50,  net. 

MITCHELL  (JOHN  K.).  REMOTE  CONSEQUENCES  OF  INJURIES  OF 
NERVES  AND  THEIR  TREATMENT.  12mo.,  239  pages,  12  illustrations.  Cloth, 
$1.75. 

MITCHELL  (S.  WEIR).  CLINICAL  LESSONS  ON  NERVOUS  DISEASES. 
12mo.,  299  pages,  with  17  engravings  and  2  colored  plates.     Cloth,  $2.50. 

MORROW  (PRINCE  A.).  SOCIAL  DISEASES  AND  MARRIAGE.  SOCIAL 
PROPHYLAXIS.     Octavo,  390  pages.     Cloth,  $3.00,  ne^     Just  ready. 

MUSSER  (JOHN  H.).  A  TREATISE  ON  MEDICAL  DIAGNOSIS,  for  Students 
and  Physicians.  New  (fifth )  edition,  thoroughly  revised  and  rewritten.  Octavo.  1205 
pages,  with  395  engravings,  and  63  full- page  colored  plates.  Cloth,  §6.50,  net;  leather, 
$7.50,  net ;  half  morocco.  $8.00,  net. 

NAGEL  (J.  D.)  AN  EPITOME  OF  NERVOUS  AND  MENTAL  DISEASES 
12mo.,  about  250  pages,  illustrated.  Shortly.  Lea's  Series  of  Medical  Epitomes.  See 
page  10. 

NATIONAL  DISPENSATORY.     See  Stille,  Maisch  &  Caspan,  page  14. 

NATIONAL    FORMULARY.      See  National  Dispensatory,  page  14. 

NATIONAL  MEDICAL  DICTIONARY.     See  Billings,  page  3. 

NETTLESHIP  fE.).  DISEASES  OF  THE  EYE.  Sixth  American  from  sixth 
English  edition.  Thoroughly  revised.  12mo.,  562  pages,  with  192  engravings,  5  colored 
plates.  Test-types,  Formula  and  Color-blindness  Test.     Cloth,  $2.25,  net. 

NICHOLS  (JOHN  B.)  AND  VALE  (F.  P.).  A  POCKET  TEXT-BOOK  OF 
HISTOLOGY  AND  PATHOLOGY.  12mo.  of  459  pages,  with  213  illustrations. 
Cloth,  -SI  .75,  net ;  flexible  leather,  $2.25,  net.     Lea's  Series  of  Pocket  Text-Books.     Page  12. 

NORRIS  (WM.  F.)  AND  OLIVER  (CHAS.  A.).  TEXT-BOOK  OF  OPHTHAL- 
MOLOGY. In  one  octavo  volume  of  641  pages,  with  357  engravings  and  5  colored 
plates.     Cloth,  $5 ;  leather,  $6. 

OWEN  ^EDMUND).    SURGICAL  DISEASES  OF  CHILDREN.     In  one  12mo. 

vol  lime  of  o2o  pages,  with  85  engravings  and  4  colored  plates.     Cloth,  $2.     See  Series  oj 
Clinvrjii  Manii/ih,  [iage  13. 

PARK  (WILLIAM  H.).  BACTERIOLOGY  IN  MEDICINE  AND  SURGERY 
12mo.,  688  pages,  87  engravings  in  black  and  colors,  2  colored  plates.     Cloth,  $3.00,  net. 

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PARK  (ROSWELL),  Editor.  A  TREATISE  ON  SURGERY,  by  American  Authors. 
For  Students  and  Practitioners  of  Surgery  and  Medicine.  Third  edition.  In  one 
large  octavo  volume  of  1408  pages,  with  692  engravings  and  64  plates.  Cloth,  $7.00; 
leather,  18.00,  net.  Published  also  in  2  volumes:  Vol.  I.,  General  Surgery  ;  Vol.  II.,. 
Special  or  Regional  Surgery.     Per  volume,  cloth,  $3.75,  net;  leather,  $4.75,  net. 

PEDERSEN  AND  PARKER'S  EPITOME  OF  GYNECOLOGY.  Lea's  Series  ot 
Medical  Epitomes.     See  page  10. 

PEPPER  (A.  J.).  SURGICAL  PATHOLOGY.  In  one  12mo  volume  of  511  pages, 
with  81  engravings.     Cloth,  $2.     See  Students'  Series  of  Manuals,  page  15. 

PICK  (T.  PICKERING).  FRACTURES  AND  DISLOCATIONS.  In  one  12mo. 
volume  of  530  pages,  with  93  engravings.    Cloth,  |2.    See  Series  of  Clinical  Manuals,  p.  13. 

PLAYFAIR  (W.  S.).  THE  SCIENCE  AND  PRACTICE  OF  MIDWIFERY. 
Seventh  American  from  the  ^inih  English  edition.  Octavo,  700  pages,  with  207  engrav- 
ings and  7  full  page  plates.     Cloth,  $3.75y  leather,  $4.75,  net. 

POCKET  FORMULARY.     Fifth  edition.     See  page  1. 

POCKET  TEXT-BOOK  SERIES  covers  the  entire  domain  of  medicine  in  eighteen 
volumes  of  350  to  525  pages  each,  written  by  teachers  in  leading  American  medical  col- 
leges. Issued  under  the  editorial  supervision  of  Been  B.  Gallaudet,  M.D.  ,  of  the  College 
of  Physicians  and  Surgeons,  New  York.  Thoroughly  modem  and  authoritative,  concise 
and  clear,  amply  illustrated  with  engravings  and  plates,  handsomely  printed  and 
bound.  The  series  is  constituted  as  follovvs  :  Eockwell's  Anatomy;  Collins  &  Eock- 
well's  Physiology;  Martin  &  Rockwell's  Chemistry  and  Physics;  Nichols  &  Vale's 
Histology  and  Pathology;  Schleif's  Materia  Medica  and  Therapeutics  ;  Malsbary's  Prac- 
tice; Collins  &  Davis'  Diagnosis;  Potts  on  Nervous  and  Mental  Diseases;  Gallaudet'& 
Surgery  ;  Hayden  on  Venereal  Diseases;  Grindon  on  the  Skin  ;  Ballenger  &  Wippern  on 
Eye,  Ear,  Nose  and  Throat ;  Evans'  Obstetrics  ;  Crockett's  Gynecology  ;  Tuttle  on  Dis- 
eases of  Children  ;  Zapffe's  Bacteriology;  Wicks  on  Nursing ;  Hamilton  on  Massage.  For 
separate  notices  see  under  various  authors'  names.     Special  circular  free  on  application. 

POLITZER  (ADAM).  A  TEXT-BOOK  OF  THE  DISEASES  OF  THE  EAR 
AND  ADJACENT  ORGANS.  Third  American  from  the  Fourth  German  edition. 
In  one  octavo  volume  of  896  pages,  with  346  engravings.     Cloth,  $7.50,  net. 

POSEY  (W.  C.)  AND  WRIGHT  (JONATHAN).  A  TREATISE  ON  THE 
EYE,  NOSE,  THROAT  AND  EAR.  Octavo,  1251  pages,  richly  illustrated  with 
650  engravings  and  35  plates  in  black  and  colors.  Cloth,  $7.00;  leather,  $8.00,  net. 
Published  also  in  two  volumes.  Vol.  I.,  Posey  on  the  Eye.  Cloth,  $4.00,  net.  Vol. 
II.,  Wright  on  the  Nose,  Throat  and  Ear.     Cloth,  $3.50,  net. 

POTTS  (CHAS.  S.).  A  POCKET  TEXT-ROOK  OF  NERVOUS  AND 
MENTAL  DISEASES.  12mo.  of  455  pages,  with  88  illustrations.  Cloth,  $1.75,  net; 
flexible  leather,  $2.25,  net.     Lea's  Series  of  Pocket  Text-Books,  page  12. 

A    TEXT-BOOK   ON  MEDICINE  AND   SURGICAL  ELECTRICITY, 

Octavo,  about  350  pages,  amply  illustrated.     Shortly. 

PROGRESSIVE  MEDICINE.    See  page  1.    Per  annum,  $9.00,  in  cloth  ;  $6.00  in  paper, 

PURDY  (CHARLES  W.).  BRIGHT'S  DISEASE  AND  ALLIED  AFFEC- 
TIONS OF  THE  KIDNEY.  In  one  octavo  volume  of  288  pages,  with  18  engrav- 
ings.    Cloth,  $2. 

PYE-SMITH  (PHILIP  H.).  DISEASES  OF  THE  SKIN.  In  one  12mo.  volume 
of  407  pages,  with  28  illustrations,  18  of  which  are  colored.     Cloth,  $2. 

RALFE  (CIIARLES  H.).  CLINICAL  CHEMISTRY.  In  one  12mo.  volume  of 
314  pages,  with  16  engravings.     Cloth,  $1.50.     See  Students'  Series  of  Manuals,  page  14. 

REMSEN  (IRA).  THE  PRINCIPLES  OF  THEORETICAL  CHEMISTRY. 
Fifth  edition  thoroughly  revised.     In  one  12mo.  volume  of  326  pages.     Cloth,  $2. 

REYNOLDS  (EDWARD)  AND  NEWELL  (F.  S.).  MANUAL  OF  PRACTICAL 
OBSTETRICS.     Octavo,  531  pages,  253  engravings  and  3  plates.     Cloth,  $3.75,  net. 


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mCHARDSON  (MA.URICE  H.).    A  PRACTICAL  TREATISE  ON  ABDOMI- 

NAL  SURGERY.      Octavo,  about  800  pages,  profusely  illustrated  with  engravings 
and  colored  plates.     Preparing. 

RICHARDSON   (BENJAMIN  WARD).     PREVENTIVE  MEDICINE.    In  one 

octavo  volume  of  729  pages.     Cloth,  §4. 

ROBERTS  (JOHN  B.).     THE  PRINCIPLES  AND  PRACTICE  OF  MODERN 

SURGERY.     Second  edition.     In  one  octavo  volume  of  838  pages,  with  474  engravings 
and  8  plates.     Cloth,  §4.25,  net;  leather,  $5.25,  net. 

ROBERTS  (SIR  WILLIAM).  A  PRACTICAL  TREATISE  ON  URINARY  AND 
RENAL  DISEASES,  INCLUDING  URINARY  DEPOSITS.  Fourth  American 
from  the  fourth  London  edition.     Octavo,  609  pages,  81  illustrations.     Cloth,  $3.50. 

ROCKWELL  (W.  H.,  Jr.).  A  POCKET  TEXT-BOOK  OF  ANATOMY.  12mo., 
60 J  pages  illustrated.  Cloth,  §2.25;  flexible  leatlier,  $2.75,  net.  Lea's  Series  of  Pocket 
Text-Books.     Page  12. 

ROGER  (G.  H.).  INFECTIOUS  DISEASES.  Translated  bv  M.  S.  Gabriel,  M.D. 
Octavo,  ^^U  pages,  41  illustrations.     Cloth,  $5.75,  net.     Just  ready. 

ROSS  (JAMES).  THE  DISEASES  OF  THE  NERVOUS  SYSTEM.  Octavo, 
726  pages,  with  184  engravings.     Cloth,  $4.50;  leather,  $5.50. 

SCHAFER  ( EDWARD  A. ) .  THE  ESSENTIALS  OF  HISTOL  OGY,  DESCRIP- 
TIVE AND  PRACTICAL.  Sixth  edition.  Octavo,  426  pages,  with  463  illustra- 
tions.    Cloth,  $3,  net. 

A    COURSE    OF  PRACTICAL    HISTOLOGY.     Second  edition.     In    one 

12mo.  volume  of  307  pages,  with  59  engravings.     Cloth,  $2.25. 

SCHALEK  (ALFRED).  AN  EPITOME  OF  DERMATOLOGY.  12mo.,  225 
pages,  34  illustrations.     Cloth,  $1.00,  n«/.     Lea' s  Series  of  Medical  Epitomes.    See  page  10. 

SCHLEIF  (WM.).  A  POCKET  TEXT-BOOK  OF  MATERIA  MEDIC  A, 
THERAPEUTICS,  PRESCRIPTION  WRITING,  MEDICAL  LATIN  AND 
MEDICAL  PHARMACY.  Second  edition.  12mo.,  380  pages.  Cloth,  $1.75; 
flexible  leather,  $2.25,   net.     Lea' s  Series  of  Pocket  Text- Books.     Page  12. 

SCHMAUS  (HANS.)  AND  EWING  (JAMES).  PATHOLOGY  AND  PATH- 
OLOGICAL ANATOMY.  Sixth  edition.  Octavo,  602  pages,  with  351  illustrations, 
including  34  colored  inset  plates.     Cloth,  §4.00,  net. 

SCHMIDT  (LOUIS  E.1.  AN  EPITOME  OF  GENITO-URINARY  AND  VENE- 
REAL DISEASES.  12mo,  249  pages,  21  illustrations.  Cloth,  $1.C0,  7iet.  Lea's 
Series  of  Medical  Epitomes.     See  page  10. 

SCOTT  (R.  J.  E. ).     See  State  Board  License  Examination  Series.     Page  14. 

SENN  (NICHOLAS).  SURGICAL  BACTERIOLOGY.  Second  edition.  In  one 
octavo  volume  of  268  pages,  with  13  plates,  10  of  which  are  colored,  and  9  engravings. 
Cloth,  $2. 

SERIES  OF  CLINICAL  MANUALS.  A  Series  of  Authoritative  Monographs  on 
Important  Clinical  Subjects,  in  12mo.  volumes  of  about  550  pages,  well  illustrated.  The 
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Pick  on  Fractures  and  Dislocations,  $2.  For  separate  notices,  see  under  various 
authors'  names. 

SERIES  OF  MEDICAL  EPITOMES.    See  page  10. 

SERIES  OF  POCKET  TEXT-BOOKS.     See  page  12. 

SERIES  OF  STATE  BOARD  LICENSE  EXAMINATIONS.    See  page  14. 

SERIES  OF  STUDENTS'  MANUALS.    See  page  15. 

SIMON  'CHARLES  E.).  CLINICAL  DIAGNOSIS,  BY  MICROSCOPICAL 
AND  CHE.MICAL  METHODS.  Fifth  edition,  thoroughly  revised.  Octavo,  695 
pages,  with  150  engravings  and  22  full-page  plates  in  colors.    Cloth,  $4. 00,  net.     Just  ready. 

PIIYSIOLOGKJAL   CHEMISTRY.     In    one    octavo  volume    of   453    pages. 

Cloth,  $3.25,  net. 


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SIMON  (W.).  MANUAL  OF  CHEMISTRY.  A  Guide  to  Lectures  and  Laboratory 
Work,  A  Text-book  specially  adapted  for  Students  of  Medicine  and  Pharmacy.  Seventh 
edition.  In  one  8vo.  volume  of  613  pages,  with  64  engravings  and  8  plates  showing 
colors  of  64  tests  and  a  spectia  plate.     Cloth,  |3.00,  net. 

SLADE(D.  D.).  DIPHTHERIA  ;  ITS  NATURE  AND  TREATMENT.  Second 
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SMITH  (J.  LEWIS).  THE  DISEASES  OF  INFANCY  AND  CHILDHOOD. 
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with  273  illustrations  and  4  full-page  plates.     Cloth,  $4.50  ;  leather,  $5.50. 

SMITH  (STEPHEN).  OPERATIVE  SURGERY.  Second  and  thoroughly  revised 
edition.     In  one  octavo  vol.  of  892  pages,  with  1005  engravings.     Cloth,  $4;  leather,  $5. 

SOLLY    (S.    EDWIN).     A    HANDBOOK    OF  MEDICAL    CLIMATOLOGY. 

Octavo,  462  pages,  with  engravings  and  11  full-page  plates.     Cloth,  $4.00. 

STARR  (M.  ALLEN).  A  TREATISE  ON  ORGANIC  NERVOUS  DISEASES. 
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STENHOUSE'S  EPITOME  OF  PATHOLOGY.  Lea's  Series  of  Medical  Epitomes. 
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STILLE  (ALFRED).  CHOLERA;  ITS  ORIGIN,  HISTORY,  CAUSATION, 
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THERAPEUTICS  AND  MATERIA  MEDICA.    Fourth  and  revised  edition 


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STILLE  (ALFRED),  MAISCH  (JOHN  M.)  AND  CASPARI  (OHAS.  JR.). 
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Pharmacy,  Actions  and  Uses  of  Medicines,  including  those  recognized  in  the  latest  Phar- 
macopoeias of  the  United  States,  Great  Britian  and  Germany,  with  numerous  references 
to  the  French  Codex.  Fifth  edition,  revised  and  enlarged  in  accordance  with  and  embrac- 
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STIMSON  (LEWIS  A.).  A  MANUAL  OF  OPERATIVE  SURGERY.  Fourth 
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A  TREATISE  ON  FRACTURES  AND  DISLOCATIONS.     Third  edition. 


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STUEGES  (OCTAVIUS).  AN  INTRODVCTION  TO  TEE  STUDY  OF  CLIN- 
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SUTER  (W.  NORWOOD).  A  MANUAL  OF  EFFRACTION  AND  MOTILITY. 
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SUTTON  (JOHN  BLAND).  SURGICAL  DISEASES  OF  TEE  OVARIES 
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ume of  513  pages,  with  119  engravings  and  5  colored  plates.     Cloth,  $3. 

SZYMONOWICZ  (L.)  AND  MacCALLUM  ( J.  BRUCE^.  A  TEXT-BOOK  OF 
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TAYLOR  (ALFRED  S.).  MEDICAL  JURISPRUDENCE.  From  the  twelfth 
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A    CLINICAL   ATLAS    OF    VENEREAL   AND    SKIN    DISEASES. 


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A  manual  of  experimental  phys_iolop,yl 


